In 2022 , Frontier Airlines reported 20.26 customer complaints for each 100,000 enplanements on domestic-scheduled operations. This was the highest rate of customer complaints among U.S. carriers.

In the United States, the airline that frequently receives the highest volume of consumer complaints is Frontier Airlines, often followed closely by Spirit Airlines. According to data from the U.S. Department of Transportation (DOT), ultra-low-cost carriers (ULCCs) tend to have higher complaint rates per 100,000 passengers due to their "unbundled" pricing models, which can lead to frustration regarding baggage fees, seat assignments, and limited customer service during flight disruptions. However, in terms of sheer "total number" of complaints, large legacy carriers like American Airlines and United Airlines often see high figures simply because they fly significantly more passengers than their smaller rivals. In 2026, a major trend in complaints involves flight cancellations and refund delays, which has prompted the DOT to implement stricter "automatic refund" rules. While budget airlines take the brunt of the criticism for their service levels, the major carriers are more frequently called out for issues related to lost baggage and technical delays. To avoid being a statistic, savvy travelers in 2026 prioritize airlines like Delta Air Lines and Southwest, which consistently rank highest in customer satisfaction and lowest in formal DOT complaints.