Only three of 46 US military aircraft types hit their annual readiness goals most years over the past decade, according to a new report from the US Government Accountability Office (GAO).

Of those three, only the US Air Force’s (USAF) UH-1N (Huey) helicopter met its annual missional capable goal for every year between 2011 and 2019. The Huey was followed by the US Navy’s submarine-hunting EP-3E Aries II – achieving its readiness goals in seven of the nine years.

The third aircraft to meet its readiness goals was another navy aircraft the E-6B Mercury airborne command and control platform.

Of the US Military branches, only the US Army saw the average annual mission-capable rate increase for some of its platforms. Across the Air Force, Navy, and Marine Corps, mission-capable rates fell on average over the past decade.

More concerningly, over half of the aircraft examined – 24 – never once met their annual readiness goals in the past decade. These aircraft include the F-22 Raptor stealth fighter jet, The US Army’s CH-47 Chinook fleet, the US Navy’s F/A-18E/F Super Hornets and US Marine Corps’ MV-22B Osprey aircraft.

Only three of the 12 rotary-wing aircraft audited met their goals at least once, and only seven of 13 fighter jet aircraft achieved the same.

The F-35 Joint Strike Fighter only achieved its mission-capable goals in two of the past eight years.

The GAO report explains the importance of the metric, reading: “The mission capable rate – the percentage of total time when the aircraft can fly and perform at least one mission – is used to assess the health and readiness of an aircraft fleet.”

The GAO also reported that for fiscal year 2018, the US paid out $49bn in operating and support (O&S) costs for the listed aircraft. Twenty of the aircraft examined saw their O&S costs increase over the past decade.

Earlier this year, the USAF backed away from readiness goals set by former Secretary of Defense Jim Mattis, after failing to meet the targets. The goals set by the then Pentagon head were designed to boost the readiness of the USAF’s F-35s, F-22s, and F-16s. None of the aircraft hit the target.