(NBC News) — On the travel-heavy day after Christmas, Southwest Airlines canceled more than 2,800 flights, or 70% of its schedule, frustrating passengers across the nation.

And the company plans reductions for days as it works to recover from the winter weather, flying just one-third of its schedule, the company said Monday.

“Our heartfelt apologies for this are just beginning,” Southwest said in a statement Monday.

Photos and video posted to social media showed bags piling up, and federal transportation officials called the cancellations unacceptable.

“I’m angry as hell, because I see mismanagement,” Ihore Konrad told NBC Chicago.

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