BALTIMORE, MARYLAND - OCTOBER 11: Travelers wait to check in at the Southwest Airlines ticketing counter at Baltimore Washington International Thurgood Marshall Airport on October 11, 2021 in Baltimore, Maryland. Southwest Airlines is working to catch up on a backlog after canceling hundreds of flights over the weekend, blaming air traffic control issues and weather. (Photo by Kevin Dietsch/Getty Images)

ATLANTA (AP) — Hundreds of flights worldwide were cancelled by midday Sunday, adding to the mounting number of scrubbed flights during the busy Memorial Day holiday weekend. Just over 1,000 flights had been canceled as of 11 a.m. EDT Saturday, according to tracking website FlightAware. That follows more than 2,300 cancellations Friday and another 1,500 on Saturday. More than 250 of Sunday’s cancellations involved aircraft scheduled to fly to or from U.S. cities. Delta Air Lines cancelled the most flights among major U.S. airlines. Delta said Saturday’s cancellations were because of bad weather and “air traffic control actions.”