United made an offer for substantial bonus miles for flights taken during the first quarter of 2004 — as much as quintuple miles for top elites.

Then they changed the wording of the offer, to make the bonus top out at quadruple miles. But many flyers saw the original offer, which was advertised on the United website and in USA Today.

After much prodding, United has agreed to honor the original terms of the bonus — but only for those flyers who know about the bait and switch. So you need to register to get them to stand by the terms of their original offer. And do it quickly — it isn’t clear how long the registration link will be valid.

Gene Fowler, who has done yoeman’s work in getting United to honor their offer, has a website with more details on the story.