Chris Kattan allegedly committed an anti-masker act onboard American Airlines flights, scaring other passengers and prompting staff to order him out of the plane... TMZ has learned.According to sources with direct knowledge, the former 'SNL' star boarded Monday's flight from Dallas/Fort Worth (LAX) but his sudden appearance surprised many passengers who were sitting next him in first class.According to passengers, Chris seemed to be stumbling and sick. This was partly due to mucous sticking out of his nose as he leaned forward. We were told that he was not wearing any mask at the time. Passengers alerted the flight attendants, who brought him paper towels and asked him to put on a mask.According to Chris, he did wear one -- the federal travel mask mandate is still in force -- but it was below his nose. By now, his behavior was causing anxiety among other passengers. Witnesses claim that he begged flight attendants to not boot him and even asked them if they'd ever seen him on "SNL."Multiple times, staff asked him to remove his mask and warned that if he didn’t, they would call the police. He finally stood up and left.