U.S. travelers report that American Airlines is the most unreliable airline in the world when measured by the total flight problems and reported complaints in 2022.

Determining which airline has the "most" mechanical issues is difficult because the data can be measured in two ways: by the sheer number of incidents or by the "rate" of incidents relative to the number of flights. Larger airlines like American Airlines, United, and Delta often report the highest total number of mechanical delays or cancellations simply because they fly thousands of more flights per day than smaller carriers. However, when looking at industry data from the Bureau of Transportation Statistics (BTS), smaller regional carriers or "Ultra Low-Cost Carriers" (ULCCs) sometimes show a higher percentage of delays due to maintenance issues because they have smaller fleets and fewer "spare" planes available to swap in when a problem arises. In recent years, certain airlines operating older fleets—such as some regional partners flying for the big three—have faced more scrutiny. It is important to distinguish between "mechanical issues" (which are often minor things like a faulty light or a stuck valve) and "safety issues." In the U.S. and Europe, maintenance standards are so strictly regulated that an airline with a genuine pattern of unsafe mechanical failures would be grounded by the FAA or EASA. Therefore, while an airline might have frequent "technical delays," it doesn't necessarily mean the airline is unsafe; rather, it often means their maintenance teams are being very conservative and catching issues before they ever leave the gate.