"The US Air Force proposed to divest - [that is] retire - its F-22 Block 20 aircraft without fully documenting the implications," the report said on Tuesday. "Block 20s are used for training and aren't upgraded with the same capabilities as the rest of the fleet."
Block 20 Raptors have not been upgraded with advanced air-to-ground attack capabilities, more advanced radar, improved cockpit displays and AIM-9X and AIM-12D missiles like the rest of the F-22 fleet, the report said.
"In its proposal to Congress, the Air Force didn't note key details such as how to train without Block 20s or whether they should be upgraded instead of retired. Congress didn't have enough data to make a decision," the report added.
Lockheed Martin, the aircraft's prime contractor, estimated that upgrades would cost at least $3.3 billion and take approximately 15 years to complete but did not provide supporting data either, according to the report.