At a Glance
In this report, the Congressional Budget Office analyzes the recent availability, use, and operating and support costs of stealthy F-35 fighter aircraft. Programwide operating and support costs exceeded $5 billion in 2023. The F-35 has three variants: the F-35A, operated by the Air Force; the F-35B, operated by the Marine Corps; and the F-35C, operated primarily by the Navy.
Availability and Use. As F-35s have aged, their availability and use have decreased, CBO finds. The availability and use of F-35s have been lower, in some cases much lower, than those of other fighter aircraft of the same age. For example, the average availability rate of a 7-year-old F-35A has been about the same as that of a 36-year-old F-16C/D and a 17-year-old F-22. The availability of the Navy’s F-35Cs has been closer to that of its earlier fighter aircraft at the same age.
Operating and Support Costs. Per aircraft and per flying hour, operating and support costs of F-35s have stabilized after a period of decline, CBO finds.
- F-35As. Operating and support costs per aircraft and per flying hour have been more variable than those of the Air Force’s other fighter aircraft. In recent years, costs of F-35As have been similar to those of F-15Es, below those of F-22s, and above those of F-16C/Ds.
- F-35Bs. In 2023, operating and support costs per flying hour fell below those of the Marine Corps’ AV-8B fighter aircraft for the first time.
- F-35Cs. Operating and support costs per aircraft and per flying hour generally have been higher than those of the Department of the Navy’s other fighter aircraft.
Notes About This Report
All years referred to in this report are federal fiscal years, which run from October 1 to September 30 and are designated by the calendar year in which they end.
All costs are expressed in 2023 dollars. To remove the effects of inflation, the Congressional Budget Office adjusted those costs with the gross domestic product price index from the Bureau of Economic Analysis.
An aircraft’s age refers to how long it has been since the Department of Defense took possession of that aircraft. Age 1 consists of months 1 to 12, age 2 consists of months 13 to 24, and so forth. (That counting scheme differs from traditional birthday enumeration in which, for instance, a 6-year-old child has already lived six years and is living through his or her seventh year of life.)
The availability and use data in this report come from the Air Force’s Reliability and Maintainability Information System (REMIS), the Department of the Navy’s Decision Knowledge Programming for Logistics Analysis and Technical Evaluation system (DECKPLATE), and the F-35 program office. Aircraft operating and support cost data come from the Air Force Total Ownership Cost (AFTOC) system and the Department of the Navy’s Visibility and Management of Operating and Support Cost (VAMOSC) system.
On the cover: F-35B Lightning II aircraft assigned to Marine Fighter Attack Squadron (VMFA) 121 in Subic Bay, Philippines, are secured to the flight deck as sailors man the rails aboard the amphibious assault ship USS Wasp (LHD-1) while departing in support of Exercise Balikatan 2019. Exercise Balikatan, in its 35th iteration, is an annual U.S. and Philippine military training exercise focused on a variety of missions, including humanitarian assistance and disaster relief, counterterrorism, and other combined military operations. Navy photo by Mass Communication Specialist 1st Class Daniel Barker.
Three branches of the military—the Air Force, Marine Corps, and Navy—are in the process of acquiring additional F-35 fighter aircraft. It is the Department of Defense’s (DoD’s) largest current aircraft acquisition program. The F-35 has three variants: the F-35A, operated by the Air Force; the F-35B, operated by the Marine Corps; and the F-35C, operated primarily by the Navy (though the Marine Corps operates a smaller number). The costs of operating those aircraft and their availability and use patterns will be important components of the cost and capability of the U.S. tactical aircraft fleet for many years to come. F-35s’ operating and support costs exceeded $5 billion in 2023.
This report augments earlier Congressional Budget Office reports (described below) about the F-35 in several ways.
- It analyzes two additional years of data (from 2023 and 2024) about the availability and use of F-35s and other fighter aircraft.
- It depicts the relationship between an aircraft’s age and its availability and use differently from CBO’s previous analyses.1
- It compares the operating and support costs of F-35s and other fighter aircraft through 2023. (Data for operating and support costs for 2024 were not available when this research was undertaken.)
CBO examined the availability and use of DoD’s F-35 fighter aircraft in two earlier reports: Availability and Use of F-35 Fighter Aircraft (April 2022), www.cbo.gov/publication/57842; and Availability and Use of F-35 Fighter Aircraft: An Update (February 2023), www.cbo.gov/publication/58902. Another earlier report provided insights about maintenance issues at aircraft depots as the F-35 was entering service: The Depot-Level Maintenance of DoD’s Combat Aircraft: Insights for the F-35 (February 2018), www.cbo.gov/publication/53543.
Availability and Use of F-35 Fighter Aircraft
CBO analyzed the availability and use of the three variants of F-35 aircraft, both by year and by aircraft age.
Availability Rates of F-35s
CBO measures fleet availability rates by dividing the number of hours that aircraft are both mission capable and in the possession of operational squadrons by the total number of aircraft hours for the entire fleet. (A mission capable aircraft can perform at least one of its primary training or operational missions.) The measure that CBO uses typically produces lower availability rates than the measure used by DoD. That is because CBO’s measure has a larger denominator that includes aircraft in depot maintenance status, whereas DoD generally only reports the availability rates of aircraft in the possession of operational squadrons.
Availability Rates of F-35s, by Year
Percent
Since 2022, fleetwide availability of F-35s has been in the range of 50 to 60 percent, which is lower than the program’s target availability rate of 65 percent. The services told CBO that they would like to achieve higher rates of availability.
Availability Rates of F-35s, by Age
Percent
Older F-35s have tended to have lower availability rates. The pattern is less clear for F-35Cs, perhaps caused by that fleet’s relatively small size. In 2024, DoD had approximately 400 F-35As, 140 F-35Bs, and 80 F-35Cs.
Full Mission Availability Rates of F-35s
CBO measures aircraft availability using mission capable rates. The full mission availability rate is a more stringent measure of readiness than the availability rate because the full mission availability rate reflects an aircraft’s ability to perform all—not just one or more—of its possible missions. For example, an aircraft with inoperative night vision equipment would not be fully mission capable, even though it could perform missions during the day. By construction, an aircraft’s full mission availability rate is less than or equal to its availability rate.
Full Mission Availability Rates of F-35s, by Year
Percent
Since 2016, full mission availability rates have been considerably greater for F-35As than for F-35Bs or F-35Cs.
Full Mission Availability Rates of F-35s, by Age
Percent
As all three variants of F-35s have aged, their full mission availability rates have declined, on average. For F-35Bs and F-35Cs, only the newest aircraft have generally had full mission availability rates above 10 percent.
Usage Rates of F-35s
CBO measures aircraft use in terms of flying hours per year per aircraft, both by year and by age. To calculate the number of flying hours per aircraft, CBO uses the total fleet size, not just operator-possessed aircraft. Flying an aircraft requires that the aircraft be capable of safe flight and that there is demand for it to fly. In a sense, therefore, aircraft use is a less direct measure of aircraft performance than availability rates are. The very first F-35As (in 2011 and 2012) flew fewer than 50 hours per year but, on average, F-35As flew over 200 hours in their first year (age 1).
Flying Hours per F-35 Aircraft, by Year
Hours
The 2019 Selected Acquisition Report (SAR) for F-35s had benchmarks for average flying hours: 250, 300, and 316 each year for F-35As, Bs, and Cs, respectively. No variant has yet reached those benchmarks. Subsequent to that SAR, the military services reduced their planned flying of F-35s.
Flying Hours per F-35 Aircraft, by Age
Hours
Older F-35s have tended to fly fewer hours. As with availability rates, the usage pattern is less clear for F-35Cs.
Fraction of F-35s Flying More Than 30 Hours in a Month
To complement its analysis of average flying hours per aircraft, CBO tallied the percentage of aircraft that flew more than 30 hours in a month (that is, averaged at least roughly one flying hour per day). Flying that much remains the exception, but it has been far more common for F-35Cs than for F-35As or F-35Bs. Again, hours flown can be affected by demand for an aircraft as well as the aircraft’s availability.
F-35 Aircraft Flying More Than 30 Hours in a Month, by Year
Percent
In recent years, F-35Cs have greatly surpassed the other F-35 variants in the number of months in which they have flown more than 30 hours.
F-35 Aircraft Flying More Than 30 Hours in a Month, by Age
Percent
Older F-35As and F-35Bs have been less likely than older F-35Cs to fly more than 30 hours in a month.
Operating and Support Costs of F-35s
Operating and support costs are recurring costs of operating aircraft (such as fuel and maintenance) as well as the costs of associated military personnel. This category of costs includes depot-level maintenance but excludes aircraft procurement costs and research and development costs.
Operating and support costs are reported in AFTOC (for the Air Force) and VAMOSC (for the Department of the Navy, which comprises the Navy and the Marine Corps).2 Costs in those systems are fleetwide and annual, not assigned to specific aircraft, whereas REMIS and DECKPLATE provide monthly availability and flying hours for specific aircraft. The data run through 2023; reliable data were not yet available for 2024 when this research was undertaken.
Operating and Support Costs of F-35s, by Year
Billions of 2023 dollars
In 2023, F-35As’ operating and support costs approached $3.2 billion. Such costs were much lower for the other variants because those fleets are much smaller.
Operating and Support Costs per F-35 Aircraft, by Year
Millions of 2023 dollars
Operating and support costs per F-35C aircraft are greatest, although costs for all variants have stabilized. Before 2015, costs per aircraft were more irregular and generally larger.
Operating and Support Costs per F-35 Flying Hour, by Year
Thousands of 2023 dollars
For all three variants of F-35s, operating and support costs per flying hour have stabilized and are generally similar. Before 2015, costs per flying hour were more irregular and generally larger.
F-35As Compared With Other Air Force Fighter Aircraft
In addition to the F-35A, the Air Force has other fighter aircraft: the F-15C/D, the F-15E, the F-16C/D, and the F-22. The F-35A is intended to eventually replace the F-16C/D. Like the F-35A, the F-22 is stealthy; by contrast, the F-15s and F-16s are not stealthy. Stealthy aircraft have different maintenance requirements because of the materials used on the skin of the aircraft to make them less visible to adversaries’ radar.
Availability of Air Force Fighter Aircraft
For these comparisons, CBO was able to analyze the availability of Air Force fighters back to 1990. (The F-35As’ availability rates shown here are the same as those shown previously.) To date, the availability of stealthy fighters has been lower than that of nonstealthy fighters of the same age.
Availability Rates of Air Force Fighter Aircraft, by Year
Percent
Although the F-35A is not meeting the Air Force’s availability goal, availability rates of F-35As have exceeded those of other Air Force fighter aircraft in recent years. Those other aircraft are much older than the F-35As.
Availability Rates of Air Force Fighter Aircraft, by Age
Percent
Availability rates of F-35As have been considerably below rates observed for nonstealthy Air Force fighter aircraft of the same age. For older F-35As, availability rates have also been below the rates observed for stealthy F-22s.
Usage Rates of Air Force Fighter Aircraft
On average, the Air Force’s fighter aircraft have flown between 150 and 200 hours per year. Those averages have tended to fall as the fleets have aged. Stealthy aircraft (the F-35A and the F-22) tend to fly fewer hours than nonstealthy aircraft of the same age.
Flying Hours per Air Force Fighter Aircraft, by Year
Hours
In recent years, F-35As flew more hours per aircraft than most other Air Force fighter aircraft flew.
Flying Hours per Air Force Fighter Aircraft, by Age
Hours
Use of F-35As has been considerably lower than use of nonstealthy Air Force fighter aircraft of the same age. The average use of F-35As is similar to that of F-22s starting when each of those types of aircraft hit age 5.
Operating and Support Costs of Air Force Fighter Aircraft
Data about the operating and support costs of Air Force aircraft are for the fleet as a whole. Because those costs are not available for individual aircraft, they cannot be presented by aircraft age in the same way that CBO presents availability and use data. To standardize the comparisons, CBO divided the data by the number of aircraft and by the number of hours each fleet flew in each year. The data that CBO analyzed ran through 2023.
Operating and Support Costs per Air Force Fighter Aircraft, by Year
Millions of 2023 dollars
In recent years, operating and support costs per F-35A aircraft have been similar to costs of F-15Es, even though the F-15E fleet is much older than the F-35A fleet. Stealthy F-22s have consistently had greater operating and support costs per aircraft than nonstealthy Air Force fighter aircraft.
Operating and Support Costs per Flying Hour of Air Force Fighter Aircraft, by Year
Thousands of 2023 dollars
In recent years, operating and support costs per F-35A flying hour have been similar to those of F-15C/Ds and F-15Es, although those fleets are much older than the F-35A fleet. (CBO removed early year outlier data from this figure so as to focus on more recent years’ costs.)
F-35Bs Compared With Marine Corps AV-8B Fighter Aircraft
The Marine Corps is purchasing the F-35B—a short takeoff, vertical landing fighter aircraft—to replace its AV-8B aircraft. In the mid-2000s, the Marine Corps had more than 150 AV-8Bs, but the fleet’s size had diminished to 46 in 2024. The service plans to eventually acquire 280 F-35Bs, up from its 2024 count of approximately 140.3
Availability of Marine Corps Fighter Aircraft
Availability rates of F-35Bs in recent years have exceeded those observed in the AV-8B fleet that the F-35Bs are replacing, but rates were lower than those of AV-8Bs at the same age. The AV-8B availability rates shown here come from DECKPLATE. The Department of the Navy has a newer availability data system called the Aviation Maintenance Supply Readiness Report (AMSRR).4 Those data are not used in these figures, though, because they are available only since 2018.
Availability Rates of Marine Corps Fighter Aircraft, by Year
Percent
Since 2016, availability of F-35Bs has exceeded availability of AV-8Bs
Availability Rates of Marine Corps Fighter Aircraft, by Age
Percent
Availability of F-35Bs has been considerably lower than that of AV-8Bs at the same age.
Usage Rates of Marine Corps Fighter Aircraft
As measured by flying hours per aircraft, usage rates for AV-8Bs and F-35Bs were similar in recent years—even though the AV-8B fleet was much older.
Flying Hours per Marine Corps Fighter Aircraft, by Year
Hours
Flying hours per F-35B and AV-8B aircraft were similar from 2016 through 2022.
Flying Hours per Marine Corps Fighter Aircraft, by Age
Hours
F-35Bs flew considerably fewer hours than AV-8Bs did at the same age.
Operating and Support Costs of Marine Corps Fighter Aircraft
Even as the AV-8B aircraft are being phased out, their operating and support costs per aircraft and per flying hour have remained relatively stable, though they are increasing. As aircraft fly less, fixed costs are distributed over fewer hours, increasing costs per flying hour.
Operating and Support Costs per Marine Corps Fighter Aircraft, by Year
Millions of 2023 dollars
Operating and support costs per F-35B aircraft have stabilized, but they remain above the AV-8B’s costs per aircraft. (CBO removed early year outlier data from these figures so as to focus on more recent years’ costs.)
Operating and Support Costs per Flying Hour of Marine Corps Fighter Aircraft, by Year
Thousands of 2023 dollars
In 2023, operating and support costs per F-35B flying hour fell below the AV-8B’s level for the first time. However, the AV-8B fleet is much older.
F-35Cs Compared With Other Navy Fighter Aircraft
The direct antecedent to the F-35C is the F-18 family of aircraft operated by the Department of the Navy: the F/A-18A/B, the F/A-18C/D, the F/A-18E/F Super Hornet, and the EA-18G. The F-35C is the only stealthy aircraft in that set. The F-35C is intended to replace the F/A-18C/D.
Availability of Navy Fighter Aircraft
Although the Marine Corps operates some fighter aircraft (including some F-35Cs), those aircraft are primarily operated by the Navy, so CBO grouped them under the Navy rubric. The availability rates shown below apply to all aircraft in the fleets, whether operated by the Navy or the Marine Corps. Data about the availability of F/A-18 and EA-18G aircraft come from DECKPLATE, not AMSRR.
In earlier research, CBO found that the availability of Super Hornets at age 10 was comparable to the availability of F/A-18C/D aircraft at age 20.5 The same relationship is seen in the lower figure here.
Availability Rates of Navy Fighter Aircraft, by Year
Percent
Availability rates of F-35Cs exceeded those of other Navy fighter aircraft in recent years. (Data from AMSRR, not shown here, report availability rates for the F/A-18E/F that were modestly greater than those for the F-35C in 2023 and 2024.)
Availability Rates of Navy Fighter Aircraft, by Age
Percent
Availability of F-35Cs has generally been below that of F/A-18C/Ds and F/A-18E/Fs at the same age. The differential between stealthy and nonstealthy Navy aircraft is smaller than that observed for Air Force fighter aircraft.
Usage Rates of Navy Fighter Aircraft
Previous CBO research found that the Navy’s fighters have flown more hours per aircraft than the Air Force’s have.6 In 2024, the F-35C (240 hours), the F/A-18E/F (221 hours), and the EA-18G (218 hours) all flew more hours per aircraft than any fleet of Air Force fighter aircraft. (The F-15E averaged 197 hours per aircraft in 2024; the F-35A, 195 hours; the F-22, 143 hours; and the F-16C/D, 122 hours.)
Flying Hours per Navy Fighter Aircraft, by Year
Hours
In recent years, use of F-35Cs has been similar to that of F/A-18E/Fs and EA-18Gs.
Flying Hours per Navy Fighter Aircraft, by Age
Hours
Use of F-35Cs has been considerably below that of most other Navy fighter aircraft at the same age, though the gap narrows for F-35Cs at age 7.
Operating and Support Costs of Navy Fighter Aircraft
For the Navy’s nonstealthy fighters, operating and support costs per aircraft and per flying hour have increased in recent years. For F-35Cs, by contrast, operating and support costs per aircraft and per flying have decreased since that variant’s introduction in 2013.
Operating and Support Costs per Navy Fighter Aircraft, by Year
Millions of 2023 dollars
Operating and support costs per F-35C aircraft remain above those of other Navy fighter aircraft. (CBO removed early year outlier data from these figures so as to focus on more recent years’ costs.)
Operating and Support Costs per Flying Hour of Navy Fighter Aircraft, by Year
Thousands of 2023 dollars
Operating and support costs per flying hour have generally been higher for the F-35C than other Navy fighter aircraft. But those costs have converged as the costs of the F-35C have declined and the costs of the Navy’s older fleets have risen.
1. In a previous report, CBO used a flexible functional form to represent the relationship between an F-35’s age, measured in months since the aircraft commenced operation, and its availability and use. See Congressional Budget Office, Availability and Use of F-35 Fighter Aircraft: An Update (February 2023), www.cbo.gov/publication/58902. For details about that functional form, which included squared and cubed terms, see Congressional Budget Office, Availability and Use of the F/A-18E/F Super Hornet Fighter Aircraft (February 2023), Appendix A, www.cbo.gov/publication/58687.
In this report, months are aggregated to years. For instance, the availability rate for an age 1 aircraft aggregates availability rates in months 1 through 12 after DoD took possession of the aircraft. That approach is more flexible. It allows availability to oscillate as an aircraft ages, for example—which could occur as an aircraft goes into and out of periodic upgrades.
As in the earlier report, CBO constrained its analysis to ages at which at least 30 percent of the fleet had been observed, which, for this report, allowed analysis of F-35s at ages 1 through 7. (That constraint reduced the potential for unrepresentative results and other problems associated with small sample sizes.) CBO observed 423 F-35As in their first month of operation but only 116 in their 84th month of operation (the last month of age 7). The oldest 4 F-35As were in their 14th year of operation in September 2024, but the performance of that small number of the very oldest aircraft may not be representative of the fleet as a whole when it reaches that age.
2. To make the AFTOC data as comparable as possible to the VAMOSC data, CBO excluded costs attributed to AFTOC’s 6.0 category (indirect support). Those costs are not included in VAMOSC. Additionally, to more accurately present F-35 operating and support costs, CBO added F-35 procurement-funded production support costs that were incurred between 2014 and 2018.
3. See Department of the Navy and United States Marine Corps, 2025 Marine Aviation Plan (January 2025), 2025-MARINE-CORPS-AVIATION-PLAN.PDF.
4. See Congressional Budget Office, DECKPLATE and AMSRR: Comparing Two Ways to Measure the Availability of F/A-18E/F Super Hornet Aircraft (July 2023), www.cbo.gov/publication/59098.
5. Congressional Budget Office, Availability and Use of the F/A-18E/F Super Hornet Fighter Aircraft (February 2023), www.cbo.gov/publication/58687.
6. Congressional Budget Office, Availability and Use of Aircraft in the Air Force and Navy (January 2022), www.cbo.gov/publication/57433.
About This Document
This report was prepared at the request of the Chairman and Ranking Member of the Subcommittee on Readiness of the House Armed Services Committee. In keeping with the Congressional Budget Office’s mandate to provide objective, impartial analysis, the report makes no recommendations.
Edward G. Keating, R. Derek Trunkey, and Nikhil Bhandarkar prepared the report with guidance from David Mosher. Jamaal Evans (formerly of CBO) and Christopher Martin provided assistance. David Austin, Ron Gecan, and Noah Meyerson offered comments. Eric J. Labs fact-checked the report.
Jennifer DiMascio of the Congressional Research Service and Evan Shockley of the Institute for Defense Analyses provided comments on an earlier draft. The assistance of external reviewers implies no responsibility for the final product; that responsibility rests solely with CBO.
Jeffrey Kling reviewed the report. Christine Bogusz edited it, and R. L. Rebach created the graphics and prepared the text for publication. The report is available at www.cbo.gov/publication/61347.
CBO seeks feedback to make its work as useful as possible. Please send comments to communications@cbo.gov.
Phillip L. Swagel
Director
June 2025