Delta CEO Ed Bastian said around 8,000 of the company's employees have contracted COVID-19 in the last four weeks amid the current winter surge in cases, The Associated Press reported.
The airline announced its full year 2021 financial results on Thursday and said the "rapidly spreading" omicron variant has significantly impacted staffing levels and disrupted travel across the industry.
However, Bastian added that Delta's operation has stabilized over the last week and returned to pre-holiday levels.
"Omicron is expected to temporarily delay the demand recovery 60 days, but as we look past the peak, we are confident in a strong spring and summer travel season with significant pent-up demand for consumer and business travel," he added on Thursday.
The airline said it lost $408 million in the final quarter of 2021 and is not expecting bookings to pick up in January or the first part of February.
"It’s always the weakest part of the year, and it's going to be that much weaker because of omicron. We need confidence in travel returning once the virus recedes," Bastian told the AP.
In a statement to The Hill, a Delta airlines spokesperson said "the omicron variant certainly affected us, and coupled with weather, our operation struggled over the holidays. It has since stabilized" and added that on Wednesday the airline "only had two mainline cancellations out of 2500 flights."
Delta Air Lines said in October that 90 percent of its workforce is vaccinated against COVID-19, even though it is not requiring employees to get the vaccine.
The Atlanta-based carrier is the only major airline that is not mandating vaccinations, but it does impose a $200 monthly surcharge on unvaccinated employees and requires them to be tested weekly for COVID-19.
Delta is not the only airline to face staffing shortages as a result of COVID-19 infections.
United CEO Scott Kirby said in a memo to staff on Monday that more than 3,000 employees are currently positive for the coronavirus and that United, which has mandated vaccines for its workforce, is reducing its "near-term schedules."
— Updated Jan. 14 at 12:07 p.m.