New York (CNN Business) Southwest Airlines continues to grapple with an "operational emergency" after an unusually high number of planes have been taken out of service.

The Dallas-based airline has been forced to cancel hundreds of flights since late last week because of mechanical problems with its fleet. Despite an "all hands on-deck" staffing policy for its mechanics, the company has not been able to resolve its problems.

Southwest LUV In a statement on Tuesday,said there was no common theme to the issues facing its 750 airplanes and it was extending a staffing protocol instituted last week to "maximize availability" of mechanics.

"We are requiring all hands on-deck to address maintenance items so that we may promptly return aircraft to service and take care of our customers," it said.

On Tuesday, more than 40 planes had maintenance issues -- more than twice the average number on a typical day. That created a domino effect, disrupting Southwest flights across the country.

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