(AP) -- Southwest passengers endured a third straight day of canceled and delayed flights as the airline struggled to resume normal operations on Friday.

Tracking service FlightStats Inc. reported that by mid-afternoon about 300 Southwest flights had been canceled and 1,200 more delayed. Southwest canceled nearly 1,500 flights and 4,500 others were delayed Wednesday and Thursday.

Southwest Airlines Co. said it was managing through lingering disruptions. It said most of Friday's cancelations were due to airline crews being unable to get to their flights after being stranded in other cities.

The airline said that a computer router failure caused several technology systems to break down on Wednesday, and backup systems didn't work as expected. It said those systems were fully restored.

The timing of the breakdown -- in the middle of the summer travel season -- made rebooking stranded customers more difficult because planes were already nearly full.

Southwest recommended that passengers delay travel until after the weekend. It said that customers with tickets for travel from Wednesday through next Tuesday would get two weeks to rebook without paying a higher fare.