In the U.S., ComparetheMarket named American Airlines the most unreliable airline overall, with a total of 6,491 complaints recorded over the last 12 months. In fact, the seven worst-performing airlines were all U.S.-based carriers: American, United, Spirit, JetBlue, Frontier, Delta, and Southwest Airlines.

In 2026, "unreliability" is typically measured by high cancellation rates and poor on-time performance. Historically and into the mid-2020s, low-cost carriers like Frontier Airlines and Spirit Airlines in the US have frequently appeared at the bottom of reliability rankings due to limited "recovery" options—if a flight is cancelled, they may not have another for days. In Europe, Ryanair and easyJet often face high delay percentages, though they rarely cancel. Conversely, legacy carriers like Air Canada and Lufthansa have faced reliability criticism in recent years due to frequent labor strikes and ground handling shortages at major hubs like Frankfurt and Toronto. For the highest reliability in 2026, travelers generally look to Delta Air Lines in North America or Qatar Airways and ANA internationally, as these carriers maintain high operational "buffer" zones to minimize passenger disruption.