And beyond airplanes, the first stealth helicopters were developed in the late 60s to early 70s and saw limited service during Vietnam. Called The Quiet Ones[2], these helicopters were painted with radar absorbing paint and had several novel mechanisms to reduce their noise, making them stealthy not only to radar but also to ground observers. They were tested over Area 51 and apparently near LA as well, so it seems likely they may have spooked some civilians at one point or another. The infamous "black helicopter" conspiracies/stories started popping up in the 70s, which doesn't seem particularly coincidental when you consider that we now know the The Quiet Ones existed.
The original Quiet Ones are long gone, but it's evident they were replaced by newer stealth helicopters that we don't yet know the names of. We can be pretty sure of this because famously one crashed during the raid on bin Laden[3].
[0] https://en.wikipedia.org/wiki/Lockheed_Have_Blue
[1] https://en.wikipedia.org/wiki/Lockheed_Senior_Prom
[2] https://en.wikipedia.org/wiki/The_Vinh_wiretap#Planning_and_...
[3] https://en.wikipedia.org/wiki/Death_of_Osama_bin_Laden#Helic...
In the northeast, the Tomahawk missile’s terrain navigation was tested out of a few air bases in the region, for example.
https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird
To be clear, a 10m^2 radar cross section is enormous compared to the F-117 (0.001 m^2) The F-117 was in a completely different league than the SR-71, but the SR-71 was in fact designed to be stealthy.
https://en.wikipedia.org/wiki/Lockheed_A-12
https://en.wikipedia.org/wiki/McDonnell_Douglas_A-12_Avenger...
The SR71 succeeded the Lockheed A12. It was hard to keep secret.
https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird
https://nationalinterest.org/blog/the-buzz/keeping-the-sr-71...
I bet this was made on purpose. USA has learned some tricks from Soviets with their "fake patterns"
F-117 wasn't a fighter, and A-12 was not a CAS aircraft. Pretty much like Kirov was not really an "auxiliary craft," and Tu-22 M-1-2-3 were all nearly completely different aircraft
Someone suggested to me a few years ago that might be the reason why the F-117 was designated that way.
https://fas.org/man/dod-101/sys/ac/f-117.htm