If you're a United Mileage Plus member and want to fly to Europe, check out this special offer.

Responding to an apparent glut of empty seats, United Airlines has started offering a discount on Mileage Plus award tickets to Europe. Reducing the miles required from 55,000 to just 40,000 is a great way to fill empty seats while at the same time removing the value of these unredeemed miles off of United's profit-challenged bottom line. As many observers such as smartertravel.com's Tim Winship have noted, "This is a great way to build goodwill for United because the seats would have gone unsold anyway, thus the real cost of flying a few extra award passengers is minimal."

United is offering a less substantial discount on Mileage Plus domestic reward redemptions, allowing bookings for 20,000 rather than the usual 25,000 miles on selected routes. Unfortunately United offers no discounts on flights out of its Chicago hub, apparently due to its fortress hub position. What are the yield managers thinking? Are all the flights out of Chicago flying at 85% occupancy?

Again, as Winship points out, not only are the routes limited, but this is a you--snooze-you-lose proposition--just nine days to commit to a trip. He raises the excellent point, "If United expects there to be plenty of seats available through May 21, why force them to book by March 18?" And there are no flights to or from Los Angeles. For New York-based Mileage Plus members, the only place you can fly is San Francisco. And United has thrown one more monkey wrench into the works. "If award travel is booked and ticketed less than 21 days prior to departure, the ticket is subject to an additional non-refundable close-in processing fee of up to $100 per award ticket."

In the hyper-competitive airline marketplace, don't be too surprised to see similar offers soon from United's primary competitors, Delta, American, and Continental.