New York (CNN Business) In its latest marketing stunt, Burger King is offering travelers whose flights are delayed free Impossible Whoppers.

Whopper after entering their delayed flight information on the "Delay Your Way" screen in the Burger King app. Between December 18 and December 30, travelers at any US airport can earn a coupon for a free meatlessWhopper after entering their delayed flight information on the "Delay Your Way" screen in the Burger King app.

uses the tactic often. Last year, it ran a deal that let app users Fast food brands often try to set themselves apart with splashy promotions or stunts. Burger Kinguses the tactic often. Last year, it ran a deal that let app users buy a one-cent Whopper if they were within 600 feet of a McDonald's. It has served a "Ghost Whopper" for Halloween and " Real Meals ," labeled with different food and colors, to poke fun at McDonald's Happy Meals.

The Impossible Whopper has been driving sales for Burger King.

This time, in addition to encouraging people to use its mobile app, Burger King is using this promotion to boost sales of its Impossible Whopper even further.

in April, and Burger King first tested the meatless burgern April, and rolled out the product nationally in August. José Cil, CEO of Burger King parent company Restaurant Brands International, said the product has been driving growth at the chain.

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