Southwest Airlines Co. raised the ante in the fight for customers in Denver on Monday, as it offered a free trip to Colorado customers who buy a higher-priced business ticket this month.
Southwest said it made the offer to note the fourth anniversary of its return to the Denver market.
Dallas-based Southwest competes in Denver against United Airlines, owned by UAL Corp., and Frontier Airlines, which is owned by Republic Airways Holdings Inc.
Southwest tried to buy Frontier out of bankruptcy last year, but lost out to Republic.
Southwest said Monday it would give Colorado members of its Rapid Rewards frequent-flier program a free ticket if they buy a "Business Select" ticket this month and use it to fly by Feb. 28. Southwest charges more for Business Select tickets but throws in a few goodies, such as priority boarding and free alcoholic drinks.
Frontier announced its own sale on Monday: fares as low as $49 each way to cities in the U.S. and Mexico. The offer runs through Jan. 13 but the airline said seats are limited _ it wouldn't say how many seats per flight will be offered at the cheapest price _ and some may require a three-night stay.
United officials did not immediately respond to a request for comment on the rivals' moves.