The normal rate of descent for a commercial aircraft is around 500-1000 feet per minute, so the 28,000 feet that United Airlines flight descended in 8 minutes is an abnormally rapid rate of descent. This could have been done in an emergency situation if there was an issue with the aircraft’s pressurization system. If the aircraft has leaked its cabin pressure, it must descend rapidly in order to maintain passenger oxygen levels, and prevent health issues from occurring.
