[holden]

Aircraft do have one or more ELT's. Life rafts from airliners also have ELTs. Even if an airliner went in for its one water landing, it would have gotten off several sweeps before it went under and it's ELT would no longer be able to be received.

I've been a member of the Civil Air Patrol, where we were sent out on SAR missions based on satellite reception of aircraft ELT signals.

HF

[USAF80]

General aviation may have satellite ELTs but those are not much use under water. Same same for any on a life raft.