DALLAS (CBSDFW.COM) – Southwest Airlines declared an “operational emergency” Friday because of an unusually high number of aircraft taken out of service.

In a statement to CBS 11, Southwest explained its usual number of out of service aircraft has doubled to about 40 per day or about 5 percent of the fleet.

This comes as the airline had to inspect 22 737 engine fuel pump filter seals.

Those planes are back in service.

But in a letter sent to supervisors, the airline called for “all hands on deck.”

Southwest said they are working to minimize any impact to travelers.

Southwest Airlines takes delivery of its first Boeing 737-800 at Dallas Love Field on March 19, 2012. (credit: Southwest Airlines)