The F-22 is considered the best fighter in the world. It was cancelled after about 200 were built because of the cost to build them. However, the F-35 has turned out to be even more expensive for the first few hundred planes and the F-35 still has almost 1,000 major and serious flaws.
There have been some advancements with improved engine technology since the F-35 was designed.
However, there does not seem to be enough technological advancement for a breakthrough sixth
The F-22 first flew 20 years ago in 1997 and the first planes were delivered in 2005.
The electronics, sensors and computers have been vastly improved. Lockheed built both the F-22 and the F35. They would want to take modern systems from the F-35 (make any fixes) and put them into a new upgraded hybrid F-22 / F-35 version.
Japan was also offered a new hybrid of the F-22 / F-35. Japan was going to invest about ten billion into developing their own stealth fighter but is interested in a joint project where the US would agree to share Lockheed technology.
Advanced engines about 25% more fuel efficient and 10% more thrust
The Adaptive Engine Transition Program will be delivering jet engines with about 45,000-pound-thrust turbofan engine prototypes. The engine’s fuel efficiency is improved by about 25% and thrust is increased by 10% with reduced engine heating.
AETP adds a third stream of cooled air around the outside of the engine that can be opened or closed to switch from fuel-efficient mode to high-performance mode and back again as the need arises. Variable cycle or adaptive cycle engines, will be able to switch between functioning as a turbojet with high-velocity thrust for supersonic performance and the lower speeds of airliner engines designed to reduce fuel consumption.