Allegiant Air will end its service to Las Vegas on Jan. 1, the manager of the Casper-Natrona County International Airport said Tuesday.

"Unquestionably, the Airport has appreciated and valued this partnership for the nine years it has been in place," Glenn Januska said.

"Although the Airport is certainly disappointed by Allegiant’s decision to discontinue service from Casper, it has been noted and commented by aviation observers that Allegiant is changing its corporate strategy by placing a greater emphasis on larger markets," Januska said.

The Las Vegas-based Allegiant Air (NASDAQ: ALGT) did not immediately return a call seeking comment.

Allegiant did not issue any statement statement announcing its withdrawal from Casper, Januska said.

Instead, a contact with the company called him on Aug. 18.

Meanwhile, was hearing from people trying to book flights in January and February who found they couldn't do so, he said.

Allegiant Air, however, has been announcing it is purchasing larger aircraft and entering larger markets such as Cincinnati and Denver, and focusing more on markets east of the Mississippi River, Januska said.

This marked a shift in its company philosophy when it started in small markets and flew people to resort areas such as Las Vegas, he said. For example, the Wilkes Barre/Scranton, Pa., International Airport recently learned of Allegiant's decision, too, he said.

Allegiant began its service in Casper in 2009. It flew to Phoenix/Mesa and to Las Vegas. By 2012, Allegiant had marked its 50,000th passenger at the airport. Sometimes the service was seasonal, sometimes it was year-round. It ended its Phoenix/Mesa service in 2013.

The company operated two airplanes with 166-passenger capacity, and had a goal of operating with a 90 percent -- or about 150 passengers, Januska said. That amounted to about 275-300 passengers a week, he said.

Whether other airlines will come to the Casper-Natrona County International Airport remains to be seen, Januska said. Any such decision would take months to make, he added. "If they did, we'd welcome them."