CBO examines the availability and use of DoD’s F-35 fighter aircraft. This report includes findings about fleet sizes, availability rates, time spent in depot-level maintenance, flying hours, and the effects of the coronavirus pandemic.
Complementing earlier research by the Congressional Budget Office, this report examines the availability and use of the Department of Defense’s (DoD’s) F-35 fighter aircraft. 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 by both the Navy and the Marine Corps.
CBO’s key findings are as follows:
Growing Fleets. DoD currently operates about 450 F-35 aircraft and plans to operate about 2,500 of them by the mid-2040s. F-35s began operating in 2011.
Aircraft Availability. The availability of F-35As and F-35Cs declined from 2015 to 2018 but increased in 2019 and 2020. (Availability is measured as the percentage of time an aircraft can be flown in training or on missions.) The availability of F-35Bs has been generally increasing since the aircraft began operating in 2012. In 2021, the availability rates of all three fleets of F-35s were higher than those of most of DoD’s other fighters. The F-35 fleets are much newer than most other fighters, and newer fleets typically have higher availability rates than older ones.
Depot-Level Maintenance. Many of the oldest F-35s have spent long periods—totaling a year or more—undergoing depot-level maintenance (that is, in-depth maintenance beyond the capability of personnel where the aircraft operate), in part because DoD had to upgrade the earliest aircraft to updated operational standards. Newer F-35s may not require as much time undergoing depot-level maintenance, because they received the upgrades when they were manufactured.
Annual Flying Hours. Total annual flying hours for each fleet of F-35s have generally increased along with fleet sizes. In recent years, F-35Cs have flown more hours per aircraft than have F-35As and F-35Bs. To date, all three fleets have flown fewer hours per aircraft per year than the average annual number of hours (over the service life of the fleet) anticipated in DoD’s plans.
Lifetime Flying Hours. All three fleets of F-35s are a mix of new aircraft with few flying hours and aircraft with more than 1,000 lifetime flying hours.
The Effects of the Coronavirus Pandemic. Although other types of DoD’s aircraft experienced increased availability and decreased flying hours during the initial months of the pandemic, there has been no consistent change in either measure for the F-35 fleets since the pandemic began.