United Airlines has been accused of exclusively assigning "young, blonde" staff to its VIP charter flights, such as those used by the NFL, according to lawsuit documents filed in California on Friday (local time).
The legal action also alleges the airline "bars older flight attendants" from working on the flights.
According to two flight attendants who have filed the lawsuit, United picks crews based "entirely on their racial and physical attributes and stereotypical notions of sexual allure".
Sharon Tesler and Kim Guillory have jointly filed the complaint and have 68 years of experience between them.
United released a statement in response to the allegations on Saturday.
"While we cannot comment on this ongoing litigation, the flight attendants included in our sports team charter program are largely representative of our overall flight attendant population in regards to age and race," the company said.
"Importantly, flight attendant eligibility to work a charter flight is based solely on performance and attendance and has nothing to do with age, race or gender."
United has exclusive contracts with over three dozen teams from the NFL, Major League Baseball (MLB), as well as national college programmes.
Bloomberg reported that crew who operate the VIP flights are paid more, stay at premium accommodation and are sometimes given tickets to games, including tickets to the Super Bowl and even on-field passes.
Tesler and Guillory alleged they had been told by managers that they were not on the "preferred list" of crew, based on team preferences.
United has said the average age of cabin crew on its sports team charter flights is 46.
The complainants are seeking financial compensation, including punitive damages.