You'll be amazed at how many airlines have sky marshalls on board even in Europe, plus many countries allow law enforcement officers and other selected people to fly carrying their weapons with them.
I am not and I donīt have problems with accepting armed sky marshalls aboard the aircraft. Problem starts when someone tries to arm the flight deck officers. Being proficient in close range gun combat is a full time job and not something you can squeezee into twice-a-year-four-hours-refresher. And thatīs my objection to whole thing: 1) unless youīre properly trained and you keep yourself in shape, youīll be more dangerous to yourself and your colleagues than potential hijacker 2)you canīt train and practice enough for close range combat if you at the same time want to be proficient in airplane operating.
So letīs leave whole things to professionals. After all, sky marshalls are not required to know how to fly an aeroplane.
From my own experience, including the left seat of the 727, one could ping-pong a passenger silly from floor to ceiling all day long with little fear other than popping an exterior lav service door.
At cruise level?!?!?!
Ever heard of bufffet margins? Or you plan for emerdesc to FL 100 and then doing your ping-pong routine?