Although there are some consistent issues throughout the aviation industry, when it comes to the passenger experience, not all airlines are created equal. According to new data from the luggage storage platform Bounce, Delta Air Lines, Hawaiian Airlines, Horizon Airlines, Alaska Airlines, and JetBlue round out the top of the list when it comes to customer favorite airlines. The research looked into data points including on-time arrivals, customer complaints, staff service, meals, seat comfort, in-flight entertainment, and maximum free baggage allowance. But while those airlines are the best in class, read on to find out which ones the research determined to be at the bottom of the list, representing the worst domestic airlines in the U.S. RELATED: This Is the Least Trusted Airline in the U.S., According to Data. Coming in at the fifth-worst spot on the list is Frontier Airlines. It logged on-time arrivals in just 69.5 percent of flights. Meanwhile, staff service and meals were both rated 2 out of 5.ae0fcc31ae342fd3a1346ebb1f342fcb RELATED: Delta CEO Just Warned This Major Change Is Coming to Flying. In fourth from last place is biggie United Airlines, with 1,448 complaints registered from Jan. to June 2021. Service and meals both got a 2 out of 5 here, as well, and that same low score was given to seat comfort and inflight entertainment. Third from last in the rankings is the world’s largest airline: American Airlines. The carrier registered even more complaints than United—American’s 1,490 complaints are the most of any carrier on the list—as well as a worse on-time percentage of 71.2 percent. RELATED: For more travel advice delivered straight to your inbox, sign up for our daily newsletter. Second to last on the list is Allegiant Air, which ranks the absolute worst for on-time arrivals, with just 56.6 percent of its flights arriving on time. (Compare that with Delta and Hawaiian at the top of the list, both of which log close to 90 percent on-time arrivals.) One way this low-cost domestic airline with headquarters in Las Vegas keeps ticket prices low is by not offering inflight entertainment, so it’s no surprise that the airline scored the lowest possible marks in that category. Coming in as the worst U.S. airline on the list? That would be Spirit. Even though the carrier offers one of the most fuel-efficient and newest fleets of domestic carriers, it ranks worst on the list with low quality of food and drink, as well as in-flight entertainment, scoring just 1 out of 5 in each category. It also ranks third for the highest total number of complaints issued from Jan. to June 2021, at 665. RELATED: Never Wear This Type of Clothing on a Plane, Experts Warn.