Delta Air Lines has been forced to cancel nearly 100 flights this Easter weekend due to a pilot shortage, according to a spokesperson for the Atlanta-based carrier on Sunday.

To get passengers where they need to go, the airline lifted its middle seat block nearly a month early to free up extra capacity on remaining flights.

A Delta spokesperson said the pilot shortage was exacerbated in part by a large number of workers who had vaccinations scheduled. A similar problem befell Piedmont Airlines during Spring Break, causing the American Eagle operator to ask its pilots to reschedule vaccine jab appointments.

"Delta teams have been working through various factors, including staffing, large numbers of employee vaccinations, and pilots returning to active status," a spokeswoman told travel commentator Gary Leff.

"We apologize to our customers for the inconvenience and the overwhelming majority have been rebooked for the same-travel day," a statement from the airline continued.

Delta has undergone two mass cancellation incidents in the last six months because of pilot shortages. The company canceled nearly 600 flights over the Thanksgiving weekend, an extremely unusual occurrence for an airline that prides itself on operational reliability.

At the time, the airline stated that an increase in COVID-19 infections was the root cause of the issue, with a significant number of pilots either sick with the illness or isolating themselves because contact tracers had marked them as a close contact with someone who had tested positive.

Now, crew scheduling has become more difficult as a result of Federal Aviation Administration regulations requiring pilots to wait at least 48 hours after receiving a shot.

Delta has briefly lifted capacity limits across flights in response to the crew shortage in order to free up seats for passengers whose flights have been canceled. The middle seat block is set to be reintroduced Tuesday before being phased out entirely on May 1.

Because of the success of the vaccination campaign, the airline previously stated that it was pleased to begin filling its planes to full capacity beginning next month.

Delta convinced nearly 2,000 pilots to retire early at the height of the pandemic, but the airline, like others, may soon need to resume recruiting new pilots due to a rebound in travel demand. Last week, rival United Airlines announced that it will begin new recruit training for about 300 pilots as early as May.