Also a commercial aircraft puts out IFF signals. Identification Friend or Foe. I don’t know if foreign airliners have that. It’s used to eliminate confusion for military aircraft and identify the aircraft to air traffic controllers. If high jackers don’t know about this it may still be picked up by satellite. Can the black box be picked up by GPS or sonar?
No, it 'squawks' on a transponder. It identifies the flight with the 4-digit code.
If high jackers don’t know about this it may still be picked up by satellite
Those doubts about the transponder were answered after 9/11. There is a hijack, emergency code, lost comm code, 7500/7700/7600. The codes are not unknown or secret.
If high jackers don’t know about this it may still be picked up by satellite.
If the transponder is under water or has no power, there is no signal.