Which Airline Is the Most Reliable?

Between weather- and software-caused operational meltdowns, U.S. airlines have struggled to deliver on reliability over the past few years.

To see which airlines kept flight disruptions to a minimum, NerdWallet dug into data from the U.S. Bureau of Transportation Statistics to analyze airlines’ on-time percentage and rates of cancellations, flight diversions, mishandled baggage, tarmac delays and involuntary denied boardings from July 2023 to June 2024.

This is the most recent data available at the time of writing. Note that this data does not include the CrowdStrike outage during July 2024.

Based on our analysis, Delta is the most reliable airline during the period from July 2023 to June 2024. Delta Air Lines performed the best in on-time percentage, flight cancellation rate and mishandled bags for the time period analyzed.

Hawaiian Airlines came in second due to its strong on-time percentage and the lowest number of flight diversions, tarmac delays and denied boardings. Southwest Airlines took bronze because of its low cancellation rate and strong performance in each of the other metrics.

Frontier Airlines lands in last place for the third straight year with a worst-in-class flight cancellation rate, second-worst on-time percentage and the highest rates of tarmac delays and denied boardings.

For this analysis, we analyzed the largest U.S. airlines by marketing carrier. That means American Airlines data includes both mainline flights as well as American Eagle flights operated by regional carriers such as Envoy Air and PSA Airlines.

We used percentages and rates to avoid penalizing airlines with more extensive operations. For example, Delta Air Lines may have had more cancellations than the smaller Frontier, but as a percentage of all operated flights, Frontier had a higher cancellation rate.

On-time percentage

An airline's on-time percentage is perhaps the most crucial statistic for determining its reliability. Unlike mishandled bags or involuntary boardings, whether or not a flight arrives on time affects every passenger on the plane.

Airlines must report to the U.S. Bureau of Transportation Statistics the percentage of their flights that arrived at the destination gate no later than 15 minutes after the scheduled arrival time. While a 15-minute delay may make tight connections even tighter, the DOT allows this 15-minute grace period when determining whether or not a flight is “on time.”

On-time percentages, by marketing carrier:

Based on BTS data, only two airlines topped an 80% on-time percentage from July 2023 to June 2024: Delta Air Lines at almost 84% and Hawaiian Airlines with almost a 82% on-time record. United and Alaska round out the top four with just under 80% on-time percentage.

JetBlue and Frontier almost tied as the worst performers, both with just under 69% flights on time between July 2023 and June 2024.

Flight cancellations

While delayed flights cause stress, a canceled flight can wreak even more havoc to travel plans. At best, you'll be delayed a couple of hours. However, a flight cancellation on a less-frequent route could mean a multi-day delay, buying overpriced airport food and even finding last-minute overnight lodging.

Which airlines have the fewest cancellations? BTS data shows a virtual tie between Delta and Southwest. Both canceled 0.83% of their scheduled flights from July 2023 to June 2024.

The worst performer was Frontier Airlines, which had a 2.17% cancellation rate. To put that in a different perspective, Frontier canceled around one in 46 scheduled flights during this period compared to one out of every 120 scheduled Delta or Southwest flights.

Cancellation rates, by marketing carrier:

Note that DOT flight cancellation data only includes flights canceled seven days or less before departure. That means this metric doesn't penalize airlines that reschedule or cancel flights more than a week ahead of departure — which has seemingly become increasingly common.

Mishandled luggage

Do you check or carry on your bags? If you only pack a carry-on, you might not mind how often airlines lose travelers' bags.

However, how well an airline handles checked baggage is an important factor for those who want to travel with full-size toiletries, traveling on longer trips or who just don't want to lug their luggage through the airport.

Delta comes out on top yet again. From July 2023 to June 2024, Delta mishandled just 0.42% of checked bags, according to BTS data. JetBlue and Spirit performed almost as well with a 0.43% mishandled rate. Southwest just missed the virtual podium with a 0.44% mishandle rate.

Mishandled luggage rate, by marketing carrier:

For yet another year, American Airlines was the worst-performing U.S. airline when it comes to mishandling checked bags. However, it's worth noting that American Airlines improved year-over-year, with 0.77% mishadled rate this year vs. 0.87% rate in last year's analysis.

Flight diversions

Perhaps even worse than a canceled flight is when a flight is diverted to an airport other than the destination airport. Unfortunately, this isn't as rare as you might think. Across the nine U.S. airlines analyzed, a whopping 12,400 flights were diverted between July 2023 and June 2024. That's around 1 in every 420 scheduled flights.

Perhaps thanks to the relatively nice whether of the Hawaiian islands, Hawaiian Airlines was the best performer with just 0.09% of its flights being diverted. That means just one in 1,093 Hawaiian Airlines flights was diverted during the period analyzed.

For the third straight year in NerdWallet's analysis, JetBlue had the highest diversion rate. From July 2023 to June 2024, over 1,000 JetBlue flights were diverted for a rate of 0.41%. Alaska had the second-worst luck with 0.29% flights diverted.

Flight diversion rate, by marketing carrier:

Other performance metrics

To round out our review, we analyzed the number of long tarmac delays and involuntary denied boardings from July 2023 to June 2024.

A "tarmac delay" is when a flight sits on the ground for over three hours on a domestic flight or over four hours on an international flight. From July 2023 to June 2024, Hawaiian Airlines didn't have a single tarmac delay.

On the flip side, Frontier had the highest percentage of tarmac delays — with an average of 1.23 tarmac delays for every 10,000 flights. But, the worst tarmac delay goes to United with a more-than-seven-hour tarmac delay at Austin airport on a diverted flight from Mexico City to Houston.

An involuntary denied boarding happens when an airline oversells a flight and doesn't get enough volunteers to take a different flight. Delta recorded just one involuntary denied boarding for the 12 months analyzed, while Hawaiian Airlines denied boarding to 10 passengers. On the other hand, Frontier had the highest rate of involuntary denied boardings, with 2.75 for every 10,000 passengers.

Methodology

For this analysis, we looked at several types of operations data from the U.S. Bureau of Transportation Statistics that captured performance of U.S. airlines from July 2023 to June 2024.

Here is our full dataset: