Very suspicious for a radio failure. Loss of range, power off, indicates that it's not vibration related. Thoughts include a failed crystal in the Rx, PC board land failure, broken solder joint or lead, internal problem with battery pack like a failed cell, wiring issues with the switch harness, maybe antenna pulled loose from Rx. I would, one at a time, replace the Rx, the switch, and the battery trying to isolate it. Less likely:unplug all the servos and and put them back one at a time. If it works with the first one, keep adding them until you find one causing problems. Try transmitter with another working airborne pack in case it isn't the plane radio that's the trouble. Something seems to have failed in the radio.