Jet fuel prices are rising as the war in the Middle East disrupts global oil supplies, putting cost pressure on airlines as the busy summer travel season approaches. Experts say it’s not a question of if airfares will go up, but when, for how long and by how much. The impact may be felt most on long-haul international routes, which burn significantly more fuel than shorter flights. Some airlines outside of the US have announced fare increases or fuel surcharges in an effort to offset the growing expense.