A union representing pilots for several major U.S. airlines warned that COVID-19 vaccine mandates could trigger chaos during the upcoming holiday travel season. Allied Pilots Association President Eric Ferguson, in a letter (pdf) to the White House and Congress, said that some pilots “are unable to undergo vaccination for documented medical reasons, while others are reluctant to get vaccinated based upon concerns about the potential for career-ending side effects.” The Allied Pilots Association represents about 14,000 pilots with American Airlines. As a result, Ferguson asked for an exemption to President Joe Biden’s pending vaccine mandate that he announced earlier this month, stipulating that private businesses with 100 employees or more get the vaccine or submit to regular testing. “To ensure commercial aviation’s ongoing viability by avoiding a scenario in which airlines are forced to either offer unpaid leaves of absence or, worse, implement mass terminations of unvaccinated pilots, it is essential …