I've heard/read a couple of times that there are air marshals on every international flight. But this doesn't seem to make much sense. Maybe they're only on flights that go to important cities like London, NYC, etc. How common are air marshals anyways?
While a FAM could be on your next flight, don't bet on it.
"There are around 30,000 commercial flights per day over the U.S.," says Casaretti. "If you were to attempt to place a team of just two FAMs on each flight, it would require an agency of over 75,000 FAMs (accounting for training and days off). FAMs cover a very small percentage of commercial flights."