The Casper-Natrona County International Airport tallied another record last month, airport director Glenn Januska said Thursday.

Nearly 8,600 people boarded planes in September, a 10.4 percent increase compared to September 2014, Januska said.

"Our September passenger number was certainly helped by the Allegiant Air Service to Las Vegas, the first September they have flown out of Casper since 2009," he said.

Until this year, Allegiant maintained a seasonal schedule, with the exception of December when people flew to Las Vegas for the National Finals Rodeo. It decided to go year-round, which has made a marked difference in airport business, Januska said.

Without Allegiant's service in September, however, the number of passengers probably would have been the same as last year, he said.

Januska doesn't know, because hard data is unknown, how many local passengers use Allegiant to fly to Las Vegas as a destination, or to use the Las Vegas McCarran International Airport to connect to other flights such as direct service to Hawaii.

Except for January, passenger numbers through June were lower than 2013 and 2014. Since then, they've been substantially higher.

The high numbers in July appeared to reflect issues in the economy and air service and Riverton.

This month will give a better picture of how well the airport -- also an indicator of the local economy -- is doing, Januska said. "Are we going to see a little bit of softening here?"