Evidence?
I don't have that evidence but likely someone at Raytheon does...
“We might be the system that caught the first evidence of E.T. out there,” said Aaron Maestas, director of engineering and chief engineer for Surveillance and Targeting Systems at Raytheon's Space and Airborne Systems business. “But I’m not surprised we were able to see it. ATFLIR is designed to operate on targets that are traveling in excess of Mach 1. It’s a very agile optical system with a sensitive detector that can distinguish between the cold sky and the hot moving target quite easily.”
https://www.cia.gov/library/center-for-the-study-of-intellig...
I do believe that any qualified historian of science could point out to you topics in linguistics (origin of language), psychology (nature of consciousness), astrophysics (what's inside a black hole, if anything), and many other topics where more than 7 decades have gone by, with lots of smart people studying a topic, and yet at the end of that much time practically nothing has been learned.
The government has been studying UFOs for 7 decades
==> The government has learned something
==> The government has acquired alien technology
Check out Philip J Corso or Robert Salas, but there are , many, many others who have blown the whistle including Walter Haut the public affairs officer during the Roswell crash (and recovery).
https://en.wikipedia.org/wiki/The_Day_After_Roswell
https://www.disclose.tv/capt-robert-salas-ufos-shut-down-nuc...