https://quillbot.com/blog/frequently-asked-questions/is-it-frequent-flier-or-flyer/
Both frequent flier and frequent flyer can be used to describe someone who flies often. Most language authorities favor "flier" to refer to someone who flies.
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https://www.slashfilm.com/506573/up-in-the-air-real-life-ryan-bingham-cheats-his-way-to-lifetime-platinum-elite-frequent-flier-status/
In Jason Reitman's new dramedy Up in the Air, George Clooney plays Ryan Bingham, a man who travels around the country trying to get to ten million frequent...
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https://www.ajc.com/business/delta-changes-frequent-flier-program-award-money-spent-not-miles-flown/UNtzfYvUyEPhKlCyOiILIK/
In a major change to its frequent flier program, Delta Air Lines will soon begin awarding free flights based on dollars spent, rather than miles flown.
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