Around 2014–2015, the U.S. Navy began upgrading fighter jets like the F/A-18 Super Hornet with more advanced radar systems, especially the AN/APG-79 Active Electronically Scanned Array (AESA) radar. This upgrade is a key reason why pilots began detecting unusual objects—UAPs—on a regular basis.
It allowed pilots to see things that had likely been there all along, just hidden from previous sensor suites.
That said, just because UAP are detected doesn't mean they are extraterrestrial. At this point, they are still unidentified. But their presence in restricted or secured airspace has affected training missions.
Rear Admiral (Retired) Tim Gallaudet has testified before Congress about this, specifically recounting a secure email from Fleet Forces Command labeled “URGENT SAFETY OF FLIGHT ISSUE”, warning of multiple near-midair collisions with unidentified objects during naval exercises off the East Coast.
The software may have been tweaked, NOT the frequencies.