By Keith Laing - 04/04/11 01:19 PM EDT
At issue is a Friday flight from Phoenix to Sacramento. Less than an hour into the flight, the plane, a Boeing 737, was forced to make an emergency landing at an Air Force base in Yuma, Ariz., after its cabin lost pressure. None of the 118 passengers and five Southwest employees on board the flight was injured.
The National Transportation Safety Board and Federal Aviation Administration have begun investigating the incident.
Southwest said it operates about 300 737s overall, but only 79 were in the same subgroup of aircraft as the plane that was forced to make the emergency landing.