Casper-Natrona County International Airport saw its first passenger decrease in 18 months in July.

Airport officials say the number of passengers leaving Casper fell 1.3 percent in July compared to July of last year.

Airport manager Glenn Januska says he was surprised by the decrease, but he also says he wasn't expecting to see the double-digit increases that were seen in the first six months of 2013.

Januska says it was at around July of last year that Delta began flying larger aircraft into Casper from Salt Lake City. United also increased its frequency from Casper to Denver during the same timeframe.

“It was at about that time last year that we started to see a lot more seats on the market,” Januska said.  “We’re comparing ourselves to unconstrained numbers.”

Nearly 8,700 passengers departed from Casper last month, which Januska says is still a strong month for CPR.

Januska says the airport has seen a nearly 19 percent year-to-date passenger increase.