For starters, their primary job is to protect and ensure the safety of passengers. Therefore, training to protect and keep themselves safe from passengers seems oxymoronic on its face.
The Transportation Security Administration will once again offer self-defense classes to flight attendants and pilots as the airline industry deals with a surge in cases of unruly passengers and sometimes violent behavior on flights.
The Federal Aviation Administration has documented more than 3,000 reports of unruly passengers on flights so far this year, and 2,350 of those cases have been tied to mask-wearing disputes. It has initiated investigations into 487 of those cases, more than triple the 146 cases that were investigated in all of 2019.
(The New York Times, June 21, 2021)
Instead of forcing them to engage in armed combat with potentially infectious idiots, just arm attendants and pilots with tranquilizer guns. And have them use darts that require only a scratch to put out an elephant for a good 10-15 minutes. That should give the attendants time to zip tie (and mask if necessary) any unruly passenger.