It takes me a while for my brain to boot up, but i feel some memories coming back now. Look up "Rescue from Shangri La" on Youtube. 12 minute vintage film, and one shot of BC-611 in the use you're asking about. Years ago i read the WW2 Nat'l Geo with the original article, then went and bought the Mitchell Zuckoff book "Lost in Shangri La". The U.S. went to great effort to rescue the 3 survivors of the full 24 persons on the "tourist flight". Possibly there were similar uses to communicate with drop planes but such seem rarely documented.

Oh, BTW, remember the photo of Churchill listening with a 611 while a demonstration paratroop drop was being done ?