From my experience, I can say that all commercial flights do not monitor 121.5,
but enough of them do that a downed or stranded aircraft would have a good
chance of contacting one.

By the way, did the FAA lift the requirement for monitoring 121.5? If they
did, I don't recall seeing it. Even now, on 121.5, I still hear ATC calling
aircraft with whom they've lost communications and to warn aircraft about
possible airspace incursions .

Mark



As far as I know this NOTAM is still in effect:

!FDC 1/0329 (and FDC 1/0330 Int'l version) FDC U.S. NATIONAL
AIRSPACE SYSTEM INTERCEPT PROCEDURES. UNTIL FURTHER NOTICE
ALL AIRCRAFT OPERATING IN THE U.S. NATIONAL AIRSPACE, IF
CAPABLE, WILL MAINTAIN A LISTENING WATCH ON VHF GUARD 121.5
OR UHF 243.0. IT IS INCUMBENT ON ALL AVIATORS TO KNOW AND
UNDERSTAND THEIR RESPONSIBILITIES IF INTERCEPTED. REVIEW "AERONAUTICAL
INFORMATION MANUAL" SECTION 6, 5-6-2 FOR INTERCEPT PROCEDURES.




AIM section 6-2-5 says, in part:

d. Inflight Monitoring and Reporting.

1. Pilots are encouraged to monitor 121.5 MHz and/or 243.0
MHz while inflight to assist in identifying possible emergency
ELT transmissions. On receiving a signal, report the
following information to the nearest air traffic facility:

(a) Your position at the time the signal was first heard.

(b) Your position at the time the signal was last heard.

(c) Your position at maximum signal strength.

(d) Your flight altitudes and frequency on which the
emergency signal was heard: 121.5 MHz or 243.0 MHz. If
possible, positions should be given relative to a navigation
aid. If the aircraft has homing equipment, provide the bearing
to the emergency signal with each reported position.




Despite the NOTAM and the AIM encouragement, I'd suspect
airliners don't monitor 121.5 at all times, because the
Captain and FO are using all available
radios for needed traffic (meaning they are NOT
"capable" of monitoring 121.5 as well), and the NOTAM's
purpose is "just in case the airliner is intercepted."