A determined airline passenger helped herself to a seat upgrade three times — until a fed-up flier shamed her into retreating to coach, according to a report.

The business-class warfare on the AirAsia flight from Kuala Lumpur to Hong Kong was caught on video and posted on Facebook by hero passenger Bruce Lam, Stomp reported.

Lam and his pals were seated in the airline’s X Premium Class seats, which are similar to business class, when the middle-age woman emerged from economy and sprawled out behind them just before takeoff.

A flight attendant tried to boot her from the seats, telling her they cost extra and she could book them on her next flight if she wanted.

An argument ensued, but the woman eventually returned to her seat — only to reappear after takeoff.

She was kicked out again after bickering with the attendant but returned a third time.

“A few minutes later, the woman returned to the seats behind me again for the third time. She lay down and started playing with her phone,” Lam wrote in the Facebook post. “The stewardess told her that it wouldn’t be fair to other passengers if she could ‘upgrade’ her seat by herself, while others could not.”

That’s when the woman became irate and began yelling at the flight attendant.

Having suffered long enough, Lam stood up and yelled in Cantonese, “Just return to your seat. Once, twice, thrice, they asked you. Have you no shame?”

The woman told him it was none of his business — but relinquished the seats for the final time.

The flight staff thanked Lam and his buddies with free cups of mineral water.

“Some people will only take advantage of you if you try to be nice to them, you have to be prepared to use harsher language,” he wrote.

The date of the flight is unclear.

AirAsia declined to comment, according to Stomp.

Lam’s flight fiasco hearkens back to the “Seinfeld” episode “The Airport,” where a desperate Elaine tries to sneak into first class while flying from St. Louis to New York — only to be caught and asked to return to coach.