Air fares will decline this fall, with a significant drop in prices forecast for flights from Hartsfield-Jackson International Airport, according to a consumer airfare index.

Fares typically rise during the busy summer travel season, then decline in the fall, a trend reflected in data showing Atlanta tickets booked this month are expected to drop 7.9 percent in July compared to the June peak, according to Hopper.com.

This year’s decline will be more than seasonal, the company says.

“Lower fuel prices and increased competition from the low cost carriers look set to drive prices lower,” Hopper’s chief data scientist, Patrick Surry, said.

Hopper, which makes an air travel app, said its consumer airfare index shows fares nationally will average $248 round-trip this fall, down from the peak of $276 in June. Atlanta air fares will average $230 in June, down from $252 in June.

Average domestic air fares also will be 3.6 percent percent cheaper this fall than in 2014, the firm predicts.

Ultra low-cost carriers Frontier and Spirit Airlines have expanded in Atlanta this year, bringing more competition for Atlanta-based Delta Air Lines and Southwest Airlines. Delta is the dominant carrier at Hartsfield-Jackson and Southwest holds the No. 2 position.

Delta has seen unit revenue — the amount generated by each seat-mile flown — decline 4.5 percent in June from a year ago. Delta cited softer performance in some domestic markets, as well as pressure from foreign exchange rates and lower surcharges in international markets.

Hopper said its data shows consumers are searching for flights at a median of 33 days in advance, earlier than in the past. Its data also show that sparsely-populated states with fewer airports such as Wyoming, North Dakota and Arkansas have higher prices, with average round-trip fares of more than $400.