Thanks for a potentially helpful pointer. But how does one make use of it? With the about-to-end ATW promo for those who have occasion to fly in and out of WAS (IAD, DCA or BWI) on UA, I have found myself looking at fares that were too cheap(?!), that is <$100 "base" fare before taxes and fees. I would have been happy to pay a bit more than the S or T fare that was available, but then could not a slightly more expensive ticket, only one that would have doubled the price for the same flight/seat.

So how would you go about switching to a new ticket costing only $.01 more, or $10 more, or $50 more to save the $100 re-ticketing fee? Is this only a "theoretical" possibility?