Adds details, background on airlines fuel costs in paragraphs 3-9

By David Shepardson

WASHINGTON, June 8 (Reuters) - Fuel costs for U.S. airlines jumped 78% in April to nearly $6.5 billion compared with the year before, as the Middle East conflict drives up jet fuel prices, the U.S. Transportation Department said Monday.

Airlines' fuel costs were up 26% over March and carriers used 2.6% less fuel in April over March, USDOT said in a monthly report.

The cost per gallon of fuel in April was $4.11, up $1.81 over April 2025, USDOT added, a trend that has already had an impact on the sector. Spirit Airlines, an ultra low-cost U.S. carrier, ceased operations in May, saying rising fuel prices left it no choice.

Delta Air Lines DAL.N, United Airlines UAL.O, American Airlines AAL.O and Southwest Airlines LUV.N account for about 80% of U.S. domestic flights.

The International Air Transport Association, which represents more than 370 airlines accounting for about 85% of global air traffic, said in its annual report Sunday that it expects the industry to post a combined net profit of $23 billion in 2026, well below a previous projection of ​about $41 billion and down from $45 billion in 2025.

Average fares for flights with a U.S. origin have risen this year by as much as 31% for domestic trips and 22% for international ones, when compared to the same weeks in 2025, according to KAYAK search data.

The Middle East conflict, triggered by U.S. and Israeli airstrikes on Iran, has also forced airlines to reroute flights around closed or restricted airspace, increasing fuel burn and straining already tight capacity.

Oil prices have surged on fears of supply disruption, pushing jet fuel prices sharply higher and widening refinery margins, leaving airlines facing a steep jump in their largest cost.

IATA expects airlines' fuel bill to surge to about $350 billion this year from roughly $252 billion in 2025, with ​fuel accounting for ⁠nearly a third of operating costs.