In order to dive from an airliner you would need to be,
- in a stable altitude,
- at low air speed,
- and below about 12 000 ft (though skydiving is performed in 15000–18000 ft max).
One more thing is there won’t be enough time for us to prepare. For example, an analysis made from Air France 447 (Rio de Janeiro, Brazil to Paris) which crashed in 2009 took only 3 mins 22 secs from its peak altitude of the aircraft until impact with ocean. The flight is stalling and loses its control.
You’re panicking and trying to get your chute which itself loses a big amount of time and you need to jump from an opening, no other choice than a door. Someone should open the pressurized door and you cannot depressurize an aircraft over 12k feet since the passengers may pass out.
There is no way 90% of passengers gonna get their parachutes and be prepared in this short time.
There are several other reasons for not using parachutes in commercial jets,
1. The door of a passenger plane cannot be opened in mid-flight. Even military parachutists wait till the plane gets stable to exit.
2. Parachutes which can be used by an average person is big enough to slow down a whole airliner. This will be heavy enough, reducing payload as well as increasing the number of flights to transport the same amount of passengers.
3. An opening in an aircraft destroys the whole fuselage.
4. Each parachute may weigh 8–10 kgs and too expensive.
5. It is extremely difficult to exit an unstable aircraft cruising at 400–600 mph. Most of the novice skydivers jump from an aircraft moving at 80–100 mph
6. A jet which is cruising at 35,000 feet (almost three times higher than a typical jump) every passenger would need equipment like an oxygen tank, mask and regulator, flight suit, helmet and altimeter just to manage the thin air. Or the passengers could just pass out from hypoxia (deficiency in the amount of oxygen reaching the tissues) and wake up later.
7. Each and every passenger requires training to understand parachute usage. Not everyone is good at listening to flight attendant’s emergency situation instructions or flight safety instructions which we see daily in many flights.
8. You might be in a panic state and might need to deploy the chute manually (which is practically impossible without prior experience) and what about the impact/injuries during landing? It may be to an open ocean, jungle or desert.
9. Tickets will become expensive and we know majority of the passengers choose only cheaper aircraft sometimes.
Pilots are always our companions for our safe flight. They will do every possible thing to act during emergency situations.