I was under the impression EX was a rebadged QA, maybe with some USAF specific avionics. Part of the justification of the purchase was no development time.
The main difference between the F-15QA and the F-15EX is that the new USAF Eagles will include the Eagle Passive Active Warning Survivability System (EPAWSS). In addition, the F-15QA runs a bespoke customer Operational Flight Program (OFP) software, whereas the F-15EX will run OFP Suite 9, which dovetails with the current F-15E Strike Eagle and F-15C standard. It’s designed to promote commonality across the F-15 community. “I can see an operator that can quickly jump from platform to platform because of the commonality between the OFPs,” says Giese.
A test pilot's perspective on Qatari F-15QA trials that will pave the way to deliveries in 2021, and help the development of the USAF’s new F-15EX.