The United States domestic aviation market is heavily dominated by single-aisle narrowbody aircraft, with five major airlines accounting for the majority of these planes. American Airlines leads the pack with almost 900 narrowbodies, split between Boeing and Airbus aircraft. Other top players include legacy airlines such as Delta Air Lines and United Airlines, as well as Southwest Airlines and Alaska Airlines. Here’s a closer look at the five largest narrowbody operators in the US.

Alaska Airlines
Alaska Airlines, based in Seattle, has the fifth largest narrowbody fleet in the US, with a total of 337 aircraft. The majority of their fleet consists of Boeing 737s, in line with their “Proudly All-Boeing” slogan. This includes 79 737-900ERs and 80 737 MAX 9s, as well as 14 737-700s and 14 737 MAX 8s. These planes primarily operate flights connecting West Coast cities with destinations across the US, Canada, and Mexico. Since merging with Virgin Atlantic, Alaska has simplified its fleet by transitioning away from all Airbus aircraft and standardizing training and maintenance around the 737.

In addition to their 737 fleet, Alaska also operates 89 Embraer E175 regional jets through their regional subsidiary, Horizon Air. These planes serve smaller regional routes, mostly feeding traffic into Seattle from smaller cities on the West Coast. With an average age of just 6. 9 years, these E175s offer improved passenger comfort compared to older regional jets operated by other major airlines.

Southwest Airlines
With 800 aircraft, Southwest Airlines has one of the largest narrowbody fleets in the world and the largest Boeing 737 fleet globally. The majority of their fleet consists of 737 MAX 8s, with 310 in operation at an average age of 3. 6 years. They also operate 295 737-700s, with an average age of 19. 8 years, and 195 737-800s. While the 737-700 is aging, it remains an important part of Southwest’s network, especially on lower-demand routes. However, the airline plans to increase retirements of this model in the coming years and replace them with the 737 MAX 7, which is expected to be certified by the end of this year.

Delta Air Lines
At number three, Delta Air Lines operates the most diverse narrowbody fleet in the US, with 817 aircraft across five different aircraft families. This includes 83 Airbus A220s, 57 A319s, 46 A320s, 221 A321s, 80 Boeing 717s, 240 737s, and 90 757s. This variety of aircraft allows Delta to match the correct size of aircraft to the demand of each route.