CHICAGO (NewsNation Now) — Southwest Airlines has canceled or delayed hundreds of flights this weekend, leaving many passengers stranded during the holiday weekend. 

According to FlightAware, a website that provides real-time flight insights, Southwest canceled 808 flights on Saturday and over 1,000 flights on Sunday.

That’s 27% of the airline’s scheduled flights on the nation’s largest domestic airline. 

The airline blamed the problem on air traffic control issues and weather. In a tweet on Saturday, Southwest issued a statement asking for customers to be patient as it works through their technical problems. 

However, aviation and airline sources tell NewsNation that the ATC issues causing the cancellation of nearly 1,000 Southwest Airlines flights were actually caused by a huge number of air controllers calling in sick at the Jacksonville Air Route Traffic Control Center. 

The Jacksonville Control Center is one of the nation’s largest air traffic control centers that handle flights going to and from Florida. The sources also reported that the “sick out” relates to low morale and anger over vaccine mandates. 

The FAA released the following statement on Sunday regarding flight delays and cancelations.

The airline has not commented on whether staffing shortfalls contributed to the cancellations this weekend. 

The Dallas-based company said its workers have until Dec. 8 to get a COVID-19 vaccine or apply for a religious or medical exemption. It’s to comply with a federal vaccination mandate for employees of companies with U.S. government contracts.  

Southwest’s pilot’s union is asking a court to temporarily block the mandate until an existing lawsuit over alleged U.S. labor law violations is resolved.

The airline is asking those affected to rebook their flights and to check their flight status on