A Southwest Airlines flight leaving Denver Saturday evening was forced to make an emergency landing in Dallas due to a sudden depressurization in the cabin at 20,000 feet.

According to Fox News, flight 861 had about 120 passengers on board as it was nearing Dallas Love Field when the oxygen masks dropped from the above compartment. The flight was about 30 minutes from approach to Dallas Love when the incident happened, but the passengers were allowed to remove the masks 10-15 minutes before landing. While there were no serious injuries, some passengers were treated for ear pain. There has been no official reason for the sudden depressurization, but Southwest Airlines said in a statement that the aircraft will undergo a maintenance review.

One of the passengers, Josh Trimberger, recorded some of the incident as it was happening.

Southwest Airlines has had mechanical issues lately that have forced some of their flights to make an emergency landing. Most notably was flight 1380 on April 17th when one of the engines exploded, causing debris to pierce the plane and blowing out a window that forced a passenger to be partially sucked out of the aircraft. The passenger died from her injuries.

Southwest is the second largest carrier at DIA and offers around 209 flights a day. They are headquartered at Dallas Love Field in Dallas, Texas.