[Labyrinthos]

They should eliminate the air marshals and give guns to the pilots.

That way the pilots have to leave the relative safety of the cockpit in the event of a disturbance, which could result in the bad guys taking control of the airplane. While the pilots should be armed to defend the cockpit, the job of securing the cabin is for the air marshals.

[Reeses]

Two problems: 1) the air marshals are very often not on board, and 2) air marshals spend their whole lives waiting for something to happen to justify their existence. They eventually feel the urge to shoot a passenger to earn their paycheck, as has happened. The pilots do not have this unfulfilled desire to justify themselves.