Budget master Clark Howard posted the following at his Web site today:

If you don’t fly often enough to earn elite status with an airline, a new offer from United Airlines might be just your ticket. When you purchase a ticket online at United (or at check-in and later this year at airport kiosks), you will be offered the opportunity to upgrade your coach ticket to United’s “Economy Plus,” or a coach class seat that gives passengers an extra five inches of legroom along with a 25% mileage bonus. What’s more is that this Premier Travel option lets passengers check two pieces of baggage at no charge and use premium security and boarding lines (available at 70 U.S. airports). A second option, Premier Travel Plus (offered in 15 cities) gives passengers double mileage, access to United’s Red Carpet Club airport lounges and other benefits. United offers the following pricing examples: Washington D.C. to New York: $47 one-way Premier; $84 Plus one-way. Los Angeles-San Francisco: $56 each way Premier; $95 each way Plus. Chicago-London: $158 each way Premier; $285 each way Plus. San Francisco-Tokyo: $167 each way Premier; $298 each way Plus.

Note the text I’ve highlighted in red. If you normally check your luggage in when you travel, this promotion will save you upwards of $50 per one way trip, with the added convenience of quicker security and boarding lines. If you have long legs or you plan to do some work on your laptop during the flight, the extra few inches in seat pitch in the United Premier section of the aircraft (the front rows of coach where they’ve added a few more inches of space between rows, behind business class).

Be mindful that this only applies on one leg of your trip. If you want this convenience on your return flight as well as your outgoing flight, you’ll need to shell out money a second time.