On Thursday, Sept. 5, an astute web-watcher from Michigan spotted a Delta promotion offering 5,000 miles just for signing up with the SkyMiles program. The tip was duly posted on FlyerTalk and posts began pouring in. Then, at about 10 a.m. on Sept. 6, the text in the offer had changed. Now Delta was offering 10,000 miles for signing up.

FlyerTalkers and their ilk rushed to register friends and family, but by 12:06 the offer had dropped back down to 1,000 miles.

So, what happened? Much like residents of Roswell, New Mexico, frequent flyers shook their heads in disbelief and asked if others had seen the same thing. Some theorized about a possible (and fortuitous) typo in the ad’s text – specifically, an extra zero. Others charged that the whole affair was a hoax, conjured up by some disenfranchised traveler and still others speculated that it might just be one big misunderstanding.

But Delta has confirmed that both the 5K and 10K promotions were legit, and that those who signed up in time should see their miles post within 4-6 weeks.

The lesson? Watching the web pays off. Delta wouldn’t confirm when, or if, such a promotion would happen again, but in the words of one representative, “You never know.”