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The Boeing 727, put into service in 1963, had the distinction of a rear doorway with stairs that could be lowered so that passengers could embark and disembark at rural airports which did not have their own airstairs. As initially designed, this door could be opened even whilst in flight as it is not the usual "plug" style.

In 1971, the hijacker known as DB Cooper famously used the rear door to make his parachute escape mid-flight. According to wikipedia, the CIA also used this feature to drop passengers and supplies mid-flight.

727 ejecting DB Cooper

In the wake of the DB Cooper incident and other hijackings, the FAA mandated in 1972 that cooper vanes to be installed to prevent the opening of the rear door while in flight.

Does this make the pre-cooper 727 the last passenger airliner which had a door (either passenger or cargo) that could be normally opened while in flight without first depressurizing the entire cabin?

Small Print: There was a rear cabin, pressurized bulkhead door on the 727 that you had to transit through to get access to the ventral stairways which was in the aft, unpressurized bulkhead. The actual ventral stair door itself was not a "plug" style. Thus the ventral stairways meets the requirement of being able to open in flight (even if you couldn't get there because the rear cabin bulkhead door might not open).

Animated image from wikipedia and cc.

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    $\begingroup$ One would think they'd be glad to have a way to get a hijacker off the plane mid-flight... $\endgroup$
    – Vikki
    Feb 15, 2019 at 4:20
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    $\begingroup$ Heaven knows the DC-10 doors used to open in flight all the time. $\endgroup$
    – user2298
    Aug 23, 2019 at 3:25
  • $\begingroup$ I think you are missing the point that in the Cooper incident, the aircraft was at a rather low altitude when the rear door was opened (approx 10,000' as I recall), and Cooper may have instructed the pilots not to pressurize the a/c at all. $\endgroup$
    – quiet flyer
    Apr 4, 2022 at 14:57
  • $\begingroup$ I love that animation. It's just... perfect! $\endgroup$
    – FreeMan
    Apr 4, 2022 at 15:59
  • $\begingroup$ In the Cooper incident, the aircraft was at a rather low altitude when the rear door was opened (approx 10,000' as I recall), and Cooper undoubtedly instructed the pilots not to pressurize the a/c at all. The only reason that it's significant that the door was not a "plug" type design, is because a "plug" design could never open outwards and thus would be incompatible with an "airstairs" feature. A "plug" type door could also have been opened in (unpressurized) flight, but would be less attractive than an "airstairs" door to someone planning to jump from the a/c. $\endgroup$
    – quiet flyer
    Apr 4, 2022 at 18:27

1 Answer 1

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The door of an airplane can be opened in any of the aircraft only when the airplane is depressurized. When an airplane is pressurized, the extra pressure inside the hull of the plane forces the door outwards which in turn presses on a seal and hence, to open a door in such a configuration, where 6 p.s.i. (pounds per square inch) of pressure is acting against several square feet of the door, one would need a tremendous amount of force, and even if the door was to be opened electronically or hydraulically, one would still expect rapid decompression of the cabin after opening the door.

Hence it is categorically incorrect to claim that modern (new) airplanes can't open their doors mid flight. It is quite achievable, but after depressurizing the cabin. Here is a source for your further reading.

Edit

The following airplanes have Air-Stair installed. I'm not sure which of them has an over-ride to open this Air-Stair mid-air, but any airplane which does not have a cooper vane installed (Or any other external barrier) can open the Air-Stair midair (technically):

Lockheed L1011

Boeing VC 25

Ilyushin Il-86

DC-9/MD-80/MD-90/B-717

Boeing 737

Some modified Airbus and Boeing planes have Air-Stairs too.

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    $\begingroup$ You're exploiting a loophole in my phrasing of the question (which I should close). I don't think the 727 required depressurization to release the rear door. Thus it remains the only plane that doesn't need to be depressurized to allow a door to open. $\endgroup$
    – RoboKaren
    Jun 23, 2015 at 6:32
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    $\begingroup$ It did not need depressurizing because the exit bay door opened outwards instead of inwards (And that's why cooper vanes were installed). Also, I did not exploit the loophole, but I answered to what your question asked (Can the doors be opened? YES they can be) $\endgroup$
    – Victor Juliet
    Jun 23, 2015 at 6:34
  • $\begingroup$ I amended the question to close that loophole. $\endgroup$
    – RoboKaren
    Jun 23, 2015 at 6:38
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    $\begingroup$ If memory serves, the rear stair control handle on the 727 is behind the aft cabin door in the unpressurized area. You have to depressurize the cabin to open the stairs. $\endgroup$
    – Sports Racer
    Jun 23, 2015 at 12:46
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    $\begingroup$ You don't have to depressurize the cabin to open the stairs. You have to depressurize the cabin to open the rear cabin door that leads to the stairs. If you're hiding in the area between the rear cabin door and the stairs, you can open the stairs without depressurizing the cabin. $\endgroup$
    – RoboKaren
    Jun 25, 2015 at 5:30

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