About two-thirds of Sunday's cancellations were due to a lack of flight attendants in the right places, with almost all the remaining cancellations due to a shortage of pilots. American Airlines requires its employees in the US to be fully vaccinated with the COVID mRNA shots by November 24, 2021, or face employee termination. Earlier this month, Southwest Airlines was forced to cancel thousands of flights which cost them $75 million after pilots boycotted their vaccine mandate. American Airlines received substantial subsidiaries through the CARES Act.

American Airlines Group Inc. required its employees in the U.S. to be fully vaccinated with the COVID mRNA shots by November 24, 2021 or face employee termination. American Airlines is a major U.S. airlines company that also received substantial subsidiaries through the CARES Act. American Airlines canceled more than 1,000 flights this weekend, blaming the weather and high winds in Dallas. More than 1,500 flights were canceled since Friday. The airline scrapped more than 600 flights on Sunday, or about 12% of total flight operations.

Compare this to Dallas-based Southwest Airlines, which cut 185 flights, or 5% of its Sunday operation. After public and employee furor over forced COVID shots and massive flight cancellations, Southwest Airlines CEO reversed a policy decision in October that was to place employees not willing to take the COVID shots on unpaid leave as of a federal deadline in December 2021.