Richard Riley wrote:
In the airspace for this program, they had to leave them on all the
time, along with their transponder - which had to have a mode that I'd
never seen before, mode 3. This program wasn't for a battlefield, it

Um, serious question: are you being serious that you have never seen
Mode 3? You probably have, but by a different name. Mode 3 is your
plain vanilla 0000-7777 transponder (if it has altitude reporting
technically is is Mode 3/C).

Modes 1,2 and 4 are military systems (in the free world anyway). 1
and 2 are similar to 3, and 4 is also known as IFF (identify friend
or foe, although in function it is more like identify friend and
everyone else is a regular radar blip).