A United Airlines flight from Charlotte, N.C., to Chicago was rerouted to Indianapolis on Sunday morning after dropping 22,000 feet midair. "The pilots safely descended the aircraft from 32,000 feet to approximately 10,000 feet," ExpressJet spokesman Jarek Beem said in an email. ExpressJet is one of United's regional partners and operated the flight. "To be clear -- the aircraft was in control of the pilots at all times and at no point was there an uncommanded change in altitude." The drop was caused by an issue with the pressurization system, according to Beem. Flight 5919 left Charlotte at 6:50 a.m. and arrived safely in Indianapolis around 8:30 a.m.