More than 1,200 more flights canceled Monday

More than 1,000 U.S. flights were canceled Monday, continuing the weekend's travel chaos as the omicron variant spreads throughout the nation. 

Flight Aware reported 1,242 cancellations and more than 5,600 delays on flights into, out of or within the United States on Monday. Nearly 20% of all flights out of Seattle-Tacoma International Airport have been canceled.

Globally, more than 12,800 flights have been delayed and nearly 3,000 were canceled Monday.

The trend of cancellations continues from the weekend. On Sunday, more than 1,500 flights into, out of or within the U.S. were canceled and more than 7,100 were delayed. Across the globe, more than 6,000 flights were canceled from Friday through Sunday.

The omicron variant has not stopped travelers. The Transportation Security Administration reported screening more than 5.3 million passengers from Christmas Eve through Sunday. While this is still below pre-pandemic numbers, more passengers were screened Dec. 22, than the same day in 2019. 

Delta canceled hundreds of flights over the weekend, citing weather and omicron.

"Canceling a flight is always Delta’s last resort," Delta Chief of Operations John Laughter said. "The result is not only difficult for customers, but for our people who want nothing more than to take care of them – especially over the holidays. We sincerely apologize to everyone impacted."

United also canceled hundreds of flights, which they attributed to omicron in a memo obtained by CNN. "The nationwide spike in Omicron cases this week has had a direct impact on our flight crews and the people who run our operation," the memo stated.