Everyone knows that not all airlines are created equal, but which ones are the best? Each year, Airfarewatchdog crunches the numbers and compiles a list so that you don't have to figure that out for yourself. We rate the domestic airlines on their performance in five key areas: canceled flights, on-time arrivals, mishandled bags, denied boardings, and customer satisfaction. (If you're interested in viewing our past rankings, you can view them here, here, and here.)

Overall, things are looking good for the airlines. Customer satisfaction has increased an average of 2.9 percent—the highest the industry's seen since its peak in 1994. Travelers cite improvements to the booking and flight experiences, specifically timeliness and baggage handling, as the major reasons for the upward trend. (Note: canceled flights and on-time arrivals took a hit during the first two months of the year due to harsh winter conditions experienced by much of the nation.)

So, let's get to it. Our winner this year is (drum roll, please) Alaska Airlines! This isn't surprising, as the airline has been in the top four since we debuted our list nearly four years ago. Delta, which came in first last year and stayed in the top three this year, continues to be a standout among the other legacy carriers, which still lag behind. And for the first time ever, we've included Spirit, which the Department of Transportation (DOT) now includes in its reports. Below is an in-depth look at the rankings.

Top Airlines for Overall Performance*

1. Alaska
2. Virgin America
3. Delta
4. JetBlue
5. Southwest
6. Frontier
7. Spirit
8. American (includes US Airways)
9. United

Individual Categories

Fewest Canceled Flights**
1. Alaska - 0.70% canceled
2. Frontier - 1.56% canceled
3. Delta - 1.89% canceled
4. Spirit - 2.16% canceled
5. Virgin America - 2.62% canceled
6. United - 2.64% canceled
7. Southwest - 2.74% canceled
8. American - 4.06% canceled (American - 4.12% canceled; US Airways - 3.98% canceled)
9. JetBlue - 5.80% canceled

On-Time Arrivals***
1. Alaska - 84.82% on-time
2. Delta - 82.18% on-time
3. Virgin America - 79.36% on-time
4. Southwest - 78.36% on-time
5. American - 75.37% on-time (American - 74.86% on-time; US Airways - 76.04% on-time)
6. United - 74.56% on-time
7. Spirit - 68.52% on-time
8. JetBlue - 66.08% on-time
9. Frontier - 63.31% on-time

Fewest Mishandled Bags****
1. Virgin America - 0.94 mishandled
2. JetBlue - 1.93 mishandled
3. Spirit - 2.31 mishandled
4. Frontier - 2.56 mishandled
5. Delta - 2.74 mishandled
6. Alaska - 3.28 mishandled
7. Southwest - 3.74 mishandled
8. United - 4.60 mishandled
9. American - 4.89 mishandled (American - 5.10 mishandled; US Airways - 4.62 mishandled)

Amount of Denied Boardings*****
1. JetBlue - 4.08 denied
2. Delta - 7.14 denied
3. Virgin America - 10.01 denied
4. Alaska - 27.75 denied
5. Spirit - 39.73 denied
6. American - 44.68 denied (American - 38.24 denied; US Airways - 53.22 denied)
7. United - 51.83 denied
8. Southwest - 57.24 denied
9. Frontier - 141.12 denied

Customer Satisfaction Score******
1. JetBlue - 81
2. Southwest - 78
3. Alaska - 75
4. Virgin America - 73
5. Delta - 71
6. American - 66 (includes US Airways)
7. United - 60
8. Frontier - 58
9. Spirit - 54

*Based on airlines’ scores in all categories
**Based on DOT reports on Jan and Feb 2015 flight cancellations at all reportable airports
***Based on DOT reports on Jan and Feb 2015 on-time arrivals at all reportable airports
****Based on DOT reports on Jan and Feb 2015 mishandled baggage reports per 1K passengers
*****Based on DOT report on Oct to Dec 2014 involuntary denied boardings per 1M passengers
******Based on 2015 American Customer Satisfaction Index scores