It has been a rough Presidents Day weekend for Southwest Airlines. Since Friday, the carrier experienced more cancellations and delays than any other U.S. airline. About 100 flights were canceled for maintenance reasons, as the airline struggles to keep up with an unusually high number of aircraft taken out of service for maintenance issues.
In all, more than 40 planes a day have been out of service – that's more than double the usual average, and about 5 percent of Southwest's roughly 750-plane fleet.
Southwest faces what its own managers call an operational state of emergency, due to an unusually high number of the airline's Boeing 737s being taken out of service for maintenance.
In a memo obtained by CBS News, the airline called for all hands on deck, and warned that maintenance employees could face termination for unexcused absences.
The spike in out-of-service planes follows our "CBS This Morning" investigation into mechanics' complaints of undue pressure to put aircraft back in service faster, reports correspondent Kris Van Cleave.
It prompted Friday's "state of operational emergency" letter.
Such a declaration is not unprecedented, but it is rare.
"I think it is an indication of problems," said John Goglia, a former member of the National Transportation Safety Board. "This kind of stress on the operation is not good. It doesn't bode well for the safety of the airline."
A dozen Southwest mechanics tell CBS News co-workers felt emboldened to write up problemsinto allegations of undo pressure on mechanics at Southwest.
Also last week, Southwest had to check 22 engines to ensure the proper fuel pump filter seals (or 'O' rings) were installed.
The "operational state of emergency" memo came just days after Sens. Ed Markey and Richard Blumenthalto the FAA seeking information about its oversight of Southwest following CBS News' investigation.
"Our priorities are always first and foremost safety," Southwest's senior director of safety management, Captain Dave Hunt, told CBS News last month. "I have the highest confidence in the work that our mechanics do, and also that any issue that's brought up, any issue, is dealt with appropriately."
The airline is locked in tense contract negotiations with mechanics that have stretched on for years. The mechanics' union is expressing concern over Southwest's state of emergency memo and its "threat of termination." The memo gives the airline the ability to assign longer work hours and change staffing assignments.
The union worries it will "increase the level of coercion and further degrade safety," as "technicians will be forced to work mandatory overtime irrespective of ... fatigue."
In a statement, Southwest said it is working to minimize the impact to customers of the out-of-service planes.
The FAA said it is closely monitoring the situation.