The 10 best U.S. airlines in 2021

Travelers wearing protective masks stand in line at Ronald Reagan National Airport (DCA) in Arlington, Virginia, U.S., on Tuesday, May 25, 2021.
Stefani Reynolds | Bloomberg | Getty Images

It's been a wild ride for U.S. airlines over the last 18 months amid Covid-19-induced travel fears and restrictions, not to mention trouble with unruly passengers who refused to wear their masks. But with nearly 49% of the country fully vaccinated, travel is making a big comeback — even with the fast-spreading delta variant.

If you're ready to travel, The Points Guy (TPG) has released its annual report on the best U.S. airlines for 2021.

To determine the list the website ranked each airline in four categories using data from the Department of Transportation. Those factors include reliability (including timeliness, cancellations and baggage); experience (cabin features, lounges and customer complaints); cost (including bag and change fees) and loyalty (frequent flyer usage and award availability).

For the third straight year in a row, TPG ranked Delta Air Lines No. 1, according to the report.

"The carrier wasn't a standout in any single category — it was fifth for mishandled baggage and fourth for customer complaints submitted to the DOT, for example," the report said. "However, Delta only hit the bottom spot in a single element (affordability), otherwise maintaining solid scores across the remaining data-backed criteria we analyzed. This consistency helped push it to the top spot."

Here are the 10 best U.S. airlines, according to TPG's report and their highest and lowest performing areas:

1. Delta Air Lines

Top-performing areas: involuntary bumps from flights, lounges

Lowest-performing areas: affordability

2. Southwest Airlines

Top-performing areas: customer satisfaction, bag/change fees, award availability

Lowest-performing areas: lounges

(A Southwest spokesperson says it's honored to make the list during one of the toughest years in the airline's history and credits the Southwest employees for its success.)

3. United Airlines

Top-performing areas: route network, frequent flyer

Lowest-performing areas: affordability

4. Alaska Airlines

Top-performing areas: lounges

Lowest-performing areas: bag/change fees

5. American Airlines

Top-performing areas: family, route network

Lowest-performing areas: baggage

6. JetBlue Airways

Top-performing areas: cabin features, award availability

Lowest-performing areas: bag, change fees

7. Hawaiian Airlines

Top-performing areas: timeliness, involuntary bumps

Lowest-performing areas: customer satisfaction, route network

8. Spirit Airlines

Top-performing areas: cancellations, affordability

Lowest-performing areas: wheelchairs, scooters, bag/change fees

(A spokesperson for Spirit says it's pleased to make the list and is "looking forward to climbing higher in the years to come."

9. Frontier

Top-performing areas: cancellations, affordability

Lowest-performing areas: involuntary bumps, bag/change fees, award availability

10. Allegiant Airlines

Top-performing areas: Involuntary bumps, baggage, wheelchairs/scooters

Lowest-performing areas: timeliness, cancellations, family, frequent flyer

When contacted for comment on ranking weak spots, a spokesperson for Delta said the airline is putting customers first. A United spokesperson said the company is focused on continuing to improve customer experience. Allegiant, Frontier, Hawaiian Airlines, JetBlue and American Airlines did not immediately respond to CNBC Make It's request to comment. A spokesperson for Alaska Airlines declined to comment.

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