Air Marshall Effectiveness
Since there are not enough U.S. Air Marshals to deploy them on every flight, there will be flights with and without them. You never know whether you will have one or more on any given flight, however, during times when there is a perceived need for increased security, certain flights will be manned based on intelligence.
Air marshals were first employed before Sept. 11 and have subdued unruly passengers, sometimes with the help of other passengers. Since Sept. 11, passengers have become more aware and willing to help flight crews.
I am not aware of any instance where an Air Marshal has fired a weapon in flight. However, I'm sure I would know if there had been. I'm not even aware that a Marshal has ever had to draw a weapon. Their training generally precludes that even being necessary.
And no, I am not a Marshal or otherwise involved in law enforcement, but as a passenger or crew member, I'd be most pleased to have that extra security available in the cabin.