Originally Posted by
MarkerInbound
In addition Boeing's idea was if you ran the cabin down a couple hundred feet during the taxi out the cabin altitude would be under control during the takeoff and smoother on passenger's ears. Old DC-9s took off with 0 cabin differential pressure and while I never felt the difference the outflow valve control wheel would sometimes spin around at rotation.
The 707 had a recirculation fan. Even though the F/E had the cabin depresurrized after landing, if he forgot to pull the CB on the fan arriving at the gate, the cabin would bump a bit when the F/A opened the door.