dailynewsnblog
In 2026, single-aisle narrowbody aircraft dominate US domestic aviation, with five airlines accounting for the overwhelming majority of those aircraft. 
American Airlines leads the pack with almost 900 narrowbodies, split between 
Boeing and Airbus aircraft. As for the rest of the top five, legacy airlines like 
Delta Air Lines and 
United Airlines also operate narrowbody fleets well into the 800s, while 
Southwest Airlines and 
Alaska Airlines round out the top positions. Looking at current fleet data published both by each airline and available on planespotters.net, here’s a look at the five largest narrowbody operators in the United States, starting with the fifth biggest single-aisle fleet.
5
Alaska Airlines
337 Narrowbody Aircraft
Among major US carriers, Seattle-based Alaska Airlines operates the fifth largest narrowbody fleet in the United States, totaling 337 aircraft. The airline’s lineup consists primarily of Boeing 737 aircraft, in line with the carrier’s “Proudly All-Boeing” slogan. This breaks down to mostly 737-900ER and 737 MAX 9 aircraft, with 79 and 80, respectively. As for the other 737s, Alaska operates just 14 of both the 737-700 and 14 737 MAX 8s, along with 61 Boeing 737-800s.
While Alaska’s fleet is certainly smaller than other airlines on this list, the carrier’s 737 aircraft anchors Alaska’s mainline operations. These airframes handle the majority of flights connecting West Coast cities with destinations across the United States, as well as routes to Canada and Mexico. Over the past decade, since the carrier’s merger with Virgin Atlantic, Alaska has simplified its fleet by transitioning away from all Airbus aircraft, allowing the airline to standardize training and maintenance around the 737.
In addition to Alaska’s strong fleet of 737 aircraft, the airline’s regional subsidiary, Horizon Air, operates 89 Embraer E175 regional jets, averaging just 6.9 years old. These aircraft serve Alaska’s smaller regional routes, mostly focusing on feeding traffic into Seattle from smaller cities on the West Coast. With a relatively young average age, the E175s also offer improved passenger comfort compared to older regional jets operated by some of the other major airlines across the country. Together, Alaska’s fleet of 337 narrowbodies puts Alaska in fifth place for the largest number of narrowbody aircraft in the US.
4
Southwest Airlines
800 Narrowbody Aircraft
With 800 aircraft, Southwest Airlines operates one of the largest narrowbody fleets in the world and the largest Boeing 737 fleet globally as well. Southwest’s 800 737s break down to mostly 737 MAX 8 variants, of which the airline operates 310 examples, averaging just 3.6 years old. Behind the MAX 8, Southwest operates 295 737-700s that average 19.8 years old, although the Dallas-based carrier plans to increase retirements of the type in the coming years. Lastly, Southwest’s fleet is rounded out by 195 Boeing 737-800 aircraft, complementing the airline’s fleet of MAX 8s.
While the 737-700 is aging, it remains an important part of Southwest’s network, especially on lower-demand routes. As the smallest in the next-generation 737 family, Southwest’s 737-700s now feature 137 seats, including six rows of extra legroom seats. However, as mentioned earlier, Southwest is already phasing out the 737-700, retiring 24 aircraft since July 2025 alone. These aircraft are expected to be replaced in the future with the 737 MAX 7, which Southwest expects to be certified by the end of this year.
As for the 737-800, these aircraft are about ten years younger than Southwest’s 737-700s and are expected to continue flying alongside the airline’s growing fleet of MAX 8s and soon MAX 7s. Overall, Southwest’s simple fleet of all Boeing 737 aircraft is a defining part of the airline’s fleet strategy. Pilots can easily be moved from aircraft to aircraft, maintenance procedures are standardized, and scheduling flexibility is improved in the event of operational disruptions. As Southwest’s fleet continues to grow, it’s possible it could challenge the three legacy airlines for a top spot on the leaderboard of most narrowbody aircraft.
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3
Delta Air Lines
817 Narrowbody Aircraft
At number three, Delta Air Lines operates the most diverse narrowbody fleet in the United States, totaling 817 aircraft across five different aircraft families. The Atlanta-based airline’s fleet lineup includes 83 Airbus A220s, 57 A319s, 46 A320s, 221 A321s, 80 Boeing 717s, 240 737s, and 90 757s. This variety of aircraft offers Delta tremendous flexibility to match the correct aircraft size to the demand of each route.
The Airbus A321 and Boeing 737 fleets form the backbone of Delta’s domestic network. These aircraft operate high-frequency routes from hubs like Delta, Detroit, and New York. In fact, Delta has recently doubled down on the Airbus A321neo, opting to create a subfleet of around 20 premium-heavy aircraft with lie-flat business class seats, expected to operate routes like New York to San Francisco and Los Angeles. Meanwhile, aside from these aircraft, Delta’s growing Airbus A220 fleet, with an average age of just 4.7 years, plays an important part on thinner routes, offering an incredibly comfortable passenger experience and improved fuel efficiency.
|
Aircraft |
Total Number |
In Service |
Parked |
Average Age |
|---|---|---|---|---|
|
A220-100 |
45 |
41 |
4 |
6.3 |
|
A220-300 |
38 |
35 |
3 |
2.8 |
|
A319 |
57 |
54 |
3 |
24.1 |
|
A320 |
46 |
44 |
2 |
29.3 |
|
A321 |
127 |
127 |
7.3 |
|
|
A321neo |
94 |
85 |
9 |
2.1 |
|
B717 |
80 |
73 |
7 |
24.5 |
|
B737-800 |
77 |
74 |
3 |
24.6 |
|
B737-900ER |
163 |
160 |
3 |
10.3 |
|
B757-200 |
74 |
74 |
28.1 |
|
|
B757-300 |
16 |
15 |
1 |
23.2 |
Interestingly, older aircraft types remain an integral part of Delta’s domestic network. The Boeing 717, Airbus A319, and Airbus A320 have average ages of 24.5, 24.1, and 29.3 years, respectively. Despite their older age, Delta still sees value in operating these aircraft, predominantly on shorter routes where their increased operating costs are less of a factor. Additionally, Delta is just one of two airlines on this list that operates the Boeing 757, one of the largest narrowbody aircraft flying today. The 757 allows Delta to increase capacity on high-density leisure routes and to serve further destinations in South America.
2
United Airlines
860 Narrowbody Aircraft
Like Delta, United Airlines relies heavily on narrowbody aircraft to support its extensive domestic network, operating a total of 860 single-aisle jets. The United fleet includes 207 Airbus A320 family aircraft, split between 75 A319s, 67 A320s, and 65 A321neos. Additionally, United operates the second-largest fleet of Boeing 737s, second only to Southwest, with 592 aircraft. This includes the 737-700, 737-800, 737-900, 737-900ER, 737 MAX 8 and 737 MAX 9, with the 737-800, and 737 MAX 9 leading in quantity at 141 and 140 examples, respectively. Like Delta, United also operates the 757, although it accounts for only 66% of Delta’s fleet, with 61 757 aircraft at an average age of 27.3 years.
The Airbus A321neo is the newest addition to United’s fleet and represents a major step forward in terms of fleet modernization at the airline. With an average age of just 1.1 years, these aircraft offer improved fuel burn and improved passenger comfort compared to the airline’s legacy A320s and A319s, which are over 20 years old. Like Delta, United also plans a substantial premium configured subfleet of A321neo aircraft, dubbed the “Coastliner.” These aircraft will feature a brand-new Polaris business class suite and an improved domestic economy-plus product. United also expects to take delivery of its first Airbus A321XLR aircraft in the near future, which will open up new narrowbody long-haul routes to Europe and Latin America.
Further, with almost 600 737 aircraft, the Boeing narrowbody naturally dominates United’s domestic operations, operating most services out of major hubs like Chicago, Newark, San Francisco, and Denver. Interestingly, United also has 737 bases in the Pacific, including in Guam, where it serves numerous destinations in Asia, like Tokyo, Manila, and even Ulaanbaatar in Mongolia. The mix of sizes between the 737-700 and the 737 MAX 9 allows United flexibility to serve routes with the appropriately sized aircraft, increasing load factors and decreasing costs.
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1
American Airlines
884 Narrowbody Aircraft
Coming in at number one, the world’s largest airline by passengers carried, American Airlines, takes the crown for the largest narrowbody fleet, totaling a whopping 884 aircraft. American’s fleet leans toward Airbus single-aisle jets, accounting for 55% of the carrier’s narrowbody aircraft. This includes mostly Airbus A321 aircraft, 304 to be specific, which play a central role in American’s domestic operations. These aircraft can most often be seen operating from hubs like Philadelphia and Phoenix, which see significantly more American Airbus traffic than the airline’s other hubs. In addition to the A321, American also operates 48 A320s and 132 A319s, about 100 of which were acquired through the carrier’s merger with US Airways in 2013.
On the Boeing side, American only operates the Boeing 737-800 and Boeing 737 MAX 8, each with near identical cabin interiors featuring 16 first class recliners and 156 economy seats. American flies 303 of the 737-800 and 97 of the 737 MAX 8, largely out of hubs like New York (LGA & JFK), Miami, and Chicago O’Hare. The airline’s sizable fleet of 737s nicely complements American’s Airbus fleet, providing flexibility in medium-capacity markets.
However, the evolution of American’s Airbus fleet is more interesting than that of its 737s. In 2025, American took delivery of its first A321XLR with a brand-new business class product and updated premium economy and economy seats as well. These aircraft are already operating transcontinental routes, like New York to Los Angeles, as well as European services from New York to Edinburgh. Additionally, American operates a subfleet of A321-200s with Flagship First, Flagship Business, and economy on premium transcontinental routes. However, with the introduction of the A321XLR, American plans to phase out these special A321s, dubbed the A321T, and return them to a standard layout.
