Southwest Airlines reported Sunday it was having "technology issues" that are slowing down check-in at airports across the country.

"We are experiencing technology issues today which is requiring us to process customers manually," read a message on the company's website. "Please arrive to the airport at least two hours prior to your scheduled flight time. We have teams across the system working diligently to determine a cause. We appreciate your patience while we work to resolve the issue."

The airline, which has flights from Newark as well as LaGuardia, JFK and Philadelphia, reported that 250 of the 3600 flights scheduled to operate Sunday had been affected by the problem as of 1 p.m.

The issue was also affecting the ability to book future Southwest flights.