Denver International Airport reported an 8.3% increase in passengers in January after Southwest Airlines began service to the airport. That's a 300,000 person increase compared to the time a year before.
"Southwest certainly was a part of the increase in January," airport spokesman Steve Snyder said.
United has roughly 58% of the traffic at DEN and reported a 4% rise in traffic. Hometown carrier Frontier has about 20% of the traffic and reported a 16% increase at the same time. Denver carried 3.5 million passengers last month in all.
Like everyone else is saying, I think Denver is seeing an increase from Southwest, but it's too early to see whether this trend will stick or if it's just a temporary increase. This isn't good news, however, for United or Frontier. Almost everyone in an existing airline's a bit scared when Southwest comes to town.