Southwest Airlines’ inaugural flight from Springs to Denver is pushed from Gate 9 at the Colorado Springs Airport in March. Southwest is adding temporary service from Colorado Springs to Houston and San Antonio during the Thanksgiving and Christmas peak holiday travel periods.

The Dallas-based, low-fare giant will offer the Houston flight daily on Nov. 23-24, 28-29; Dec 23, 26-30 and Jan 2-3; and the San Antonio flight daily on Nov. 20, 23-24, 27-29; Dec. 18, 23, 26-30 and Jan. 1-3, according to a new schedule uploaded Thursday. The flights are designed to determine demand for the routes during the heaviest travel periods of the year, said Greg Phillips, aviation manager for the city of Colorado Springs.

Southwest launched service to Colorado Springs on March 11 with 13 daily nonstop flights to Midway International Airport in Chicago, Dallas Love Field Airport, Denver, Las Vegas and Phoenix. The new schedule includes no changes in those flights. The airline boarded 42,329 passengers on outgoing flights during March and April; May passenger numbers won't be available until later this month, but Phillips said traffic through the airport's security checkpoint surged during May.

Joe Nevill, the airport's air service development manager, said Southwest "has made a big investment in Colorado Springs and continues to look for opportunities to build on their initial success by expanding their service." Southwest instantly became the airport's largest carrier; it boarded 35% of all passengers leaving Colorado Springs in April, up from 30.5% in March.