The inland airport’s traffic losses are not likely to stop anytime soon. An airline plans to end daily nonstop flights in September

 The steady decline in passenger traffic at Ontario International Airport continued in June and doesn’t appear likely to slow down as Delta Air Lines plans to stop flying between the Inland region and Atlanta in September.

Traffic at the airport dropped 4.36 percent in June. It was the 15th consecutive month that fewer travelers used the airport compared to the same month a year prior. A total of 373,652 travelers flew into or out of Ontario airport in June, according to the latest statistics from Los Angeles World Airports, which owns and operates Ontario, Van Nuys and Los Angeles International airports.

Passenger traffic at the airport started to slide in 2007 and the drop doesn’t appear to be done.

Delta will stop flying nonstop between Ontario and Atlanta as of Sept. 5, confirmed company spokesman Trebor Banstetter. The airline was the only one to offer two nonstop flights a day between the airports.

He said the airline’s executives haven’t decided if the flight will return next summer. It’s the first time the airline has suspended the route for a season.

The high cost of jet fuel was the reason for the route’s suspension, Banstetter said.

"This is a lengthy route that consumes a considerable amount of fuel," he said in an email.

Delta will still offer nonstop flights between Ontario and Salt Lake City, which connects to 85 other destinations.

In the first six months of the year, the airport’s traffic has dropped by 6.39 percent compared to a year ago.

Ontario airport spokeswoman Maria Tesoro-Fermin described the figures as disappointing, but said airport officials remain optimistic that a marketing plan being developed will help.

"It’s a stable low," she said of the declines.

Earlier this month, Ontario Airport Manager Jess Romo announced that Southwest Airlines planned to add a seasonal flight between Ontario and Reno starting Jan. 6. It was the first new route announced at the airport since Southwest linked Ontario to Chicago-Midway in 2010.

The airport has been in the middle of a tug-of-war with the city of Ontario and the city of Los Angeles.

Ontario city officials have long contended that the city of LA’s ownership and management of the airport poses a conflict of interest and that the focus has been on LAX rather than improving Ontario airport’s fate. The city of Los Angeles is studying a proposal by the city of Ontario to take control of the Inland airport.

At LAX, also owned and managed by Los Angeles World Airports, traffic inched up by 1.96 percent for a total of 5.7 million passengers in June. Since January, passenger counts are up 3.58 percent compared to a year ago.