Airline chatter can get heated.

Many frequent fliers become incredibly loyal to one airline, swearing their favorite carrier is the least expensive, or most reliable, or never cancels flights at the last minute. But in an ever-changing industry, with merging companies and new baggage fees and restrictions, it’s more challenging to know which one is the top performer.

That’s where data comes in — and it can reveal the truth about which airlines are worth flying. Money compared hundreds of data points across the major domestic airlines — weighing 39 factors including the average cost, price changes, fees, customer experience, and on-time performance — to determine the country’s best (and worst). Here’s where everyone landed. (Plus: See the 20 best places to go in 2019.)

Alaska Airlines Courtesy of Alaska Airlines

1. Alaska Airlines

Avg. price per roundtrip flight: $407

Avg. price per kilometer flown: $0.16

Share of on-time arrivals: 82.70%

For the second year in a row, Alaska Airlines flew in to claim Money’s best domestic airline title.

Alaska boasts the highest customer service rating among U.S. airlines, according to Travel + Leisure, as well as some of the shortest delays. Value’s there too. The airline offers the second-lowest ticket fares among U.S. airlines, at about 16¢ per kilometer, according to Rome2Rio.

Formerly a small-market airline servicing mostly the West Coast, Alaska expanded into dozens of new markets after its merger with Virgin America in 2016. In 2018 the company announced a new nonstop route between New York City and San Jose and opened a new airport lounge in New York’s John F. Kennedy International Airport.

Alaska Airlines’ other major perk comes from its popular loyalty program, named the best for frequent fliers by industry expert FlyerTalk in 2018. Unlike with most other rewards systems, Alaska fliers can redeem their miles for flights on a number of partner airlines, such as Emirates and American. The airline also sold miles for a little bit cheaper in 2017, according to The Points Guy founder Brian Kelly.

Finally, frequent fliers agree the airline offers top-notch customer service: Alaska has won J.D. Power’s customer service survey award 11 years in a row—and the airline shows no signs of slowing down in 2019.

Southwest Airlines Stephen M. Keller—Southwest Airlines

2. Southwest

Avg. price per roundtrip flight: $396

Avg. price per kilometer flown: $0.27

Share of on-time arrivals: 78.99%

Delta Air Lines Gem Russan—Shutterstock

3. Delta

Avg. price per roundtrip flight: N/A*

Avg. price per kilometer flown: N/A*

Share of on-time arrivals: 85.62%

Spirit Airline Courtesy of Spirit Airline

4. Spirit

Avg. price per roundtrip flight: $254

Avg. price per kilometer flown: $0.15

Share of on-time arrivals: 80.63%

American Airlines Brandon Wade—American Airlines

5. American

Avg. price per roundtrip flight: $353

Avg. price per kilometer flown: $0.24

Share of on-time arrivals: 78.03%

United Airlines Courtesy of United Airlines

6. United

Avg. price per roundtrip flight: $417

Avg. price per kilometer flown: $0.33

Share of on-time arrivals: 79.77%

JetBlue Ashish Tekchandani—JetBlue

7. JetBlue

Avg. price per roundtrip flight: $389

Avg. price per kilometer flown: $0.32

Share of on-time arrivals: 70.59%

Frontier Airline Courtesy of Frontier Airline

8. Frontier

Avg. price per roundtrip flight: $311

Avg. price per kilometer flown: $0.16

Share of on-time arrivals: 68.82%

Methodology

*The average roundtrip flight for Delta was $411.60 in 2017, according to Rome2Rio, but the data provider didn’t have the necessary data for 2018. Median airfares were used for Delta’s 2019 ranking calculation instead.

Money analyzed 1,600 data points for about 80 air carriers—the nine leading domestic airlines and about 70 of the largest international airlines. Price factors were weighed most heavily in determining the rankings.

Criteria included average cost per kilometer, average price of a coach flight, and year-over-year price changes; percentage of on-time arrivals and average length of delays; and customer satisfaction ratings for food, in-flight and customer service, value, comfort, loyalty programs, and in-flight entertainment. Criteria for domestic airlines also included baggage fees and flight change fees; canceled flights, delayed flights, and delayed flights due to carrier; overall experience rating, mishandled bags, and consumer complaints; and year-over-year improvements on all of the above.

Hawaiian Airlines was excluded from domestic airlines because of a substantial lack of data.

Data providers for all three rankings include Rome2Rio, FlightStats, Skytrax, Travel + Leisure, American Customer Satisfaction Index, U.S. Department of Transportation, J.D. Power, and the airlines.