[ninenot]

Yah. They were non-pressurized because they flew low. Now tell me this: when the pilot says (incredible or not) "I've got too many holes to maintain pressure, clearance low flight" will the tower tell him to just stay high and die?

Sometimes you tech guys get all wrapped up in the trees and don't really see the forest.

[Tennessee_Bob]

Ooooo! They flew low! That explains the oxygen masks and sheepskin suits with electric heaters.

The 17s had a service altitude of around 35,000 feet - about the same cruise altitude as a modern airliner, but without the pressure body. Most missions were flown between 20,000 and 30,000 feet - from 3.7 to about 5.6 miles up - unpressurized. Go read Flying Fortress by Jablonski, and look how far away the ground is on those low altitude missions.

Even if they caused a sudden depressurization that would be no big deal.

No big deal to who?