Delta Air Lines has canceled hundreds of flights over Thanksgiving, citing staffing problems during the holiday period.

With air travel demand down by more than 50% amid the coronavirus pandemic, the Atlanta-based airline has cut its staff by thousands this year through buyouts and early retirements. Thousands more are on voluntary unpaid leave.

Delta canceled nearly 300 flights on Thanksgiving Day and 160 more on Friday.

The airline said it now expects just a couple dozen residual cancellations Saturday and hopes to get back to a normal schedule by Sunday. It added the “vast majority” of affected passengers have been rebooked for flights on the same day.

“A number of factors have pressured our ability to timely staff several dozen scheduled flights,” Delta spokesman Anthony Black said this week.

Delta is apologizing to customers and said it is contacting them with new flight details. Those affected can take the new flight, choose a different one, get a credit for future travel or seek a refund.

The airline operated about 1,420 flights Thursday and plans nearly 1,800 flights Friday.

Pilot staffing in particular is key to keeping flights running, and the timing of a vote to prevent furloughs threw some uncertainty into Thanksgiving planning.

Delta and its pilots union spent the last several months working toward a deal that would allow the airline to cut costs without cutting jobs. The union agreed to reduce pilots’ guaranteed pay by 5% and that Delta would pay 1,713 pilots at risk of losing their jobs only about a third of regular pay while not working.

The airline and the pilots union reached a tentative deal in late October and then pilots cast ballots in a vote that concluded Wednesday – the day before Thanksgiving. Of those that voted, 74% were in favor and 26% were against the cut in guaranteed pay.

If the deal hadn’t been ratified Wednesday, more than 1,700 pilots, including nearly 500 based in Atlanta, would have been furloughed effective Saturday.

The busiest days for return travel from Thanksgiving trips are Sunday and Monday.

The most cancellations came on the slowest day of the holiday period – Thanksgiving Day itself.

Delta said it is continuing to block middle seats as a safety precaution amid the pandemic even as it rebooks passengers on remaining flights.

Delta emailed those whose flights were canceled acknowledging that it fell short of its standards and saying it will provide compensation in the form of frequent flier miles or vouchers.