Which Airline Has Been the Most Reliable in 2023?

Although U.S. airlines this year hadn't experienced the kinds of mass cancellations and operational breakdowns that plagued the industry in 2022, carriers continued to struggle. Part of that is due to a record number of people flying. According to data from the Transportation Security Administration, 2023 has seen some of the highest-ever single-day numbers of people passing through airport security checkpoints.

NerdWallet reviewed data from the Bureau of Transportation Statistics about on-time percentages, cancellation rates, flight diversions, mishandled baggage, tarmac delays and involuntary denied boardings to determine the most reliable — and least reliable — domestic airlines in the U.S. in 2023.

Here's a look at performance in each category of the data.

On-time percentage

On-time percentage is the headline statistic for airline performance, since whether a flight is late, and by how much, affects every passenger on the flight. The BTS defines a flight as "on time" if it arrives at the destination gate no later than 15 minutes after the scheduled arrival time.

Based on BTS data from January to August 2023, only one airline topped an 80% on-time percentage — and just barely. Delta Air Lines had an 80.8% on-time percentage. Alaska slipped in at 79.9% for second place.

The worst performers were Frontier Airlines, with just 62.1% of flights arriving within 15 minutes of the scheduled arrival time, and JetBlue Airlines, with a 65.4% on-time percentage. That means more than 1 of every 3 JetBlue flights and nearly 2 in 5 Frontier flights was delayed by more than 15 minutes during the period reviewed.

Flight cancellations

Delayed flights are bad enough. Canceled flights are a nightmare.

BTS data from January to August 2023 reveals an unexpected winner: Allegiant Airlines canceled 0.84% of its flights during the period. Alaska Airlines was a close second with a 0.86% cancellation rate.

Frontier and JetBlue were again at the bottom of the rankings. Frontier had a 2.87% cancellation rate, with JetBlue at 2.59%. That means Frontier canceled around 1 in 35 scheduled flights, while JetBlue canceled 1 in 39.

BTS cancellation data includes only flights that are canceled within seven days of departure, when they're most likely to throw travelers' plans into turmoil. Airlines aren't penalized in this metric for canceling or rescheduling flights more than a week out — which seems to have become increasingly common.

Mishandled luggage

The more connecting flights an airline has, the more opportunities there are for luggage to get lost as bags move from plane to plane. It may not be surprising, then, that airlines with route systems that don't rely on funneling everyone through hub airports seem to perform better at luggage handling.

Allegiant takes top marks with 0.16% of checked bags mishandled from January to August 2023, according to BTS data. Put another way, only 1 of every 610 bags checked on Allegiant Airlines was lost, delayed or mishandled. Southwest Airlines placed second (0.48%), while most other airlines came in at between 0.5% and 0.6%.

Two big legacy carriers, American Airlines (0.85%) and United Airlines (0.84%), were nearly tied as the worst-performing airlines for mishandled luggage. From a raw numbers stance, American mishandled the most number of checked bags: 591,365 — an average of more than 2,433 mishandled bags per day.

Flight diversions

Having your flight diverted to an airport other than your intended destination can be as confounding as a cancellation. Across U.S. airlines that report to the U.S. Department of Transportation, 9,722 flights were diverted from January through August 2023 — around 1 in every 359 scheduled flights.

During the period examined in 2023, the airline least likely to divert a flight — both in raw numbers and percentage of flights — was Hawaiian Airlines with 53 diversions and a diversion rate of 0.09%. Frontier was a distant second with a 0.19% diversion rate.

Percentage-wise, JetBlue was the worst performer with a diversion rate of 0.45% — or 1 of every 218 scheduled flights. Meanwhile, Southwest had the most diversions in total, with a whopping 2,293 diverted flights during the period.

Other performance metrics

The last two metrics we looked at were tarmac delays and involuntary denied boardings.

A "tarmac delay" is recorded when a plane has pushed back from the gate but doesn't take off, or has landed but doesn't allow passengers to get off the aircraft, for more than three hours for a domestic flight and four hours for an international flight. From January to August 2023, Hawaiian was the only major U.S. airline without a single tarmac delay. United had the most tarmac delays, 73, including one of nearly six hours.

An "involuntary denied boarding" occurs when an airline sells more tickets for a flight than it has seats available, then doesn't get enough volunteers to take a later flight. When that happens, someone gets bumped from the flight. Allegiant and Hawaiian both didn't have any involuntary denied boardings from January to June 2023 — the most recently reported data.

At the other end of the scale, Frontier denied boarding to 5,782 passengers, and American did it to 5,033. To put those numbers in context, all other airlines combined denied boarding to a total of 2,929 passengers.

The most reliable airline of 2023

Two airlines were nearly neck-and-neck in this year's analysis, but Alaska Airlines barely edged out Delta Air Lines as the most reliable.

Alaska was buoyed by a second-place finish in on-time percentage (79.9%) and second-lowest cancellation rate (0.86%). A modest denied boarding rate and a dozen tarmac delays were enough to offset a middling mishandled baggage rate (0.59%) for first place overall.

Delta took top marks in on-time percentage (80.8%) and essentially zero denied boardings. However, its cancellation rate (1.6%) was almost double Alaska's while its baggage mishandled rate (0.53%) was only modestly better than Alaska's.

Frontier was the clear worst performer among U.S. airlines, with the worst on-time percentage (62.1%), highest cancellation rate (2.87%) and exceptionally high denied boarding rate, almost eight times that of its nearest competitor.

Meanwhile, JetBlue finished in second-to-last place with a poor showing in virtually all metrics, including the second-worst on-time percentage (65.4%) and second-highest cancellation rate (2.59%). Rounding out the bottom three was Spirit Airlines with the third-worst on-time percentage (65.94%), fourth-worst cancellation rate (2.08%) and fourth-worst mishandled bag rate (0.57%).

Methodology

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

For an airline to be eligible for our analysis, it had to be a commercial airline based in the U.S. that reports data to the Department of Transportation. Also, we ranked airlines by the "marketing carrier," not the operating carrier. That means, for example, that American Eagle flights operated by Envoy Air, Piedmont Airlines and PSA Airlines were counted toward American Airlines' totals since passengers bought their tickets as American flights.

We used percentages and rates to avoid penalizing airlines with larger operations. For example, American Airlines may have had more than five times as many cancellations as Frontier but operated more than 10 times as many flights. So, as a percentage of all operated flights, Frontier had a higher cancellation rate.