Air travelers looking for cheaper tickets may have to keep waiting. The main reason flights are so expensive right now is that airlines are facing much higher fuel bills, adding billions of dollars in costs this year and making it harder to offer low fares.

Recent federal data shows how sharply prices have moved. In the United States, airfare in June was 26.5% higher than it was a year earlier, a sign that ticket prices have remained elevated even as travelers search for deals.

Fuel is one of the biggest expenses for airlines, so swings in energy prices can quickly affect what passengers pay. With fuel prices still volatile, carriers have less room to cut fares aggressively, which helps explain why bargain flights are becoming harder to find.

That means even if fuel prices shift in the months ahead, travelers should not expect a quick return to ultra-cheap tickets. As long as airlines continue paying much more for fuel, flight prices are likely to remain under pressure.