An ejection seat is required for military plane because they are expected to be shot at.
Commercial aircraft do not have a requirement for survivability when their wing is blown off from missile fire; usually, commercial aircraft usually avoid flying in zones where they could be fired on.
Fighter aircraft have short range; one of the longest range aircraft in that category have a ferry range (zero armament, full internal AND external fuel, i.e. 3 drop tanks) is the F-15, and that is 3000 NM.
That is the range of the shortest range 737 next generation model, but with full payload/passengers.
In other words, military aircraft compromise their payload and/or range with the ejection seat, which is about as heavy as the luggage of a typical passenger.
Then, since it is equipped with lots of gadgets (drogue chute, seat belt auto release, oxygen supply, not to mention the ejector rocket system itself) anyone strapped into an ejector seat has to go through a certain number of training session before they are allowed to fly.
Then you have several safety considerations.
- fighter aircraft are most usually single seaters. Which means that when the crew escapes, the rocket blast from the seat is not cooking people seating right behind, or right besides, which would be the case in an airliner. Unless you have everyone eject at the same time, which would probably involve some interesting ejection seat collision right above.
- Then you have this interesting looking bright red handle. How are you going to ensure that kids (or complete moron adults) are not going to pull on them, just for kicks? How are you going to ensue that people will not trip on them, when leaving their seat to go to the washroom?
- ejection seats have to be fitted to the person using them. Most have a maximum weight capacity of about 250 lb (many passengers are over that weight). They also have a lower weight of occupant to remain stable, the Martin Baker Mk-10, for instance, requires the person to weight a minimum of 152 lb; too bad if you are traveling with young kids. Or you very tall friend, since they also have height restriction, usually in the range 5 ft 4 to 6 ft 4 (actually, even those values are subjected to restrictions, someone who is 6 ft 4 but with slightly longer legs in proportion than the average would have to kiss his knees and the rest of his legs good-bye as they will not be ejected with the rest of the body...)
- ejection seats users wear a helmet, and oxygen mask, and a G-suit. That is because ejection at 35000 ft altitude at 600 mph is a rather harsh experience that is not survivable without protective gear.
- ejection seats require a path to get out of the plane. Fighters have a canopy that is already hinged to board the plane and can be jettisoned just before ejection (as part of ejection sequence), except in the cases where the seat has a break-the-canopy fitting to burst through or other similar system to clear the way. Airliners have luggage compartments overhead (have you ever actually flown in your life?). People are already upset when custom and safety officials go through their luggage, imaging the passenger sitting next to you physically passing through your suitcases on the way out. And good luck passing though the structural aluminium alloy that is designed to be able to stand to the 7 pounds per square inch pressure differential.
Now, ask yourself: how often have you heard of a commercial flight where occupants could have been saved if they were to jump out in a parachute, let alone an ejection seat? Most accidents occur at low altitude, during take off and landing, and so quickly that no one, not even the pilot who is supposed to be aware of everything that is happening, have time to react and jump out.
Also consider the fact that the military uses several converted civilian planes for thinks like AWACS, fuel tanker, and cargo. None of them are fitted with ejection seats, even if they are expected to sometime have to fly in combat zones.
Have you heard of a pilot union asking for ejection seats? Do you wonder why they never did?
The answer is that it is because they know:
- it is impractical
- it is dangerous (more so than the risk of crash, in fact they would increase the rate of crash)
- it does not make any sense whatsoever
- it will not work, period