I assume it is because
I assume because it’s a NASA plane, and not USAF Military and thus not operating in secrecy, it always flies with it on. The plane itself is no big deal nowadays, it’s the military camera and sensor equipment that’s super top secret. And BTW FWIW NASA also has a 747 jumbo jet with a huge door and telescope they fly around.I'm surprised it had its locator on. How high was he?