At least three major airlines said they have canceled dozens of flights because illnesses largely tied to the omicron variant of COVID-19 have taken a toll on flight crew numbers during the busy holiday travel season.

According to the Associated Press, Germany-based Lufthansa said Friday that it was canceling a dozen long-haul transatlantic flights over the Christmas holiday period because of a “massive rise” in sick leave among pilots.

The cancellations on flights to Houston, Boston, and Washington come despite a “large buffer” of additional staff for the period. The airline says it couldn’t speculate on whether COVID-19 infections or quarantines were responsible because it was not informed about the sort of illness. Passengers were booked on other flights.



According to ABC News, The airline says it couldn’t speculate on whether COVID-19 infections or quarantines were responsible because it was not informed about the sort of illness. Passengers were booked on other flights. Lufthansa said in a statement that “we planned a very large buffer for the vacation period.

But this was not sufficient due to the high rate of people calling in sick.”U.S.-based Delta Air Lines and United Airlines said they had to cancel dozens of Christmas Eve flights because of staff shortages tied to omicron. United canceled 169 flights, and Delta called off 127, according to FlightAware.

“The nationwide spike in omicron cases this week has had a direct impact on our flight crews and the people who run our operation,” United said in a statement to several news outlets. “As a result, we’ve unfortunately had to cancel some flights and are notifying impacted customers in advance of them coming to the airport.”