Southwest Airlines fixes tech bug that delayed hundreds of flights

US airline Southwest Airlines says it has fixed the technology problems that delayed hundreds of flights on Sunday and that it expects a normal day of operations.

The Dallas company had been warning passengers flying on Monday to arrive at the airport two hours early and print boarding passes beforehand.

When asked early whether fliers should continue with those precautions, an airline spokesman said customers should expect a normal day on Monday.

Southwest used backup systems around the country on Sunday to check-in travellers lacking printed or mobile boarding passes.

Airline representatives have not said what was causing the problem, but a spokesman has said there was no indication that hackers were behind it.

There were about 450 delays out of 3,600 flights scheduled on Sunday.