A Southwest Airlines plane had to land this weekend due to a “pressurization issue in flight” that resulted in passengers being told to wear oxygen masks during the final 30 minutes in the air from Denver to Dallas, according to the airline and a report from a local TV station.
Flight 861 ultimately made an “uneventful landing” on Saturday night, with four of 120 passengers on board getting checked by paramedics “to assess ear pain,” Southwest Airlines said in a statement to Fortune. The crew of the aircraft had radioed ahead for the assistance, the airline said, before it landed at Dallas Love Field.
Southwest also told CBS News that the aircraft did not actually lose pressure, saying that the incident was “related to an aircraft duct that resulted in the oxygen masks deploying.”
The incident is not the only safety-related issue the airline has experienced recently. Last month, a woman was killed when an engine exploded during flight, making it the first airline fatality in the U.S. since 2009. Another Southwest flight diverted weeks later when a window cracked.
The aircraft in the Dallas incident “underwent a maintenance review,” Southwest said.