Passionate about promoting aviation, the beauty of flight and the science behind it, Antonio is an avid reader of aviation magazines and books, and he loves visiting airshows all over the world, taking photos and writing about airplanes and helicopters as well. He is currently based in Palermo, Sicily.
Walk through any major US airport in 2026, and the ramp seems dominated by a handful of familiar types: Boeing 737s, Airbus A320 family jets, and the occasional widebody aircraft. Look closer at airline fleet lists, though, and you'll find a few less common variants hiding in plain sight. Some are the last survivors of a once-common family, while others are unusual versions of otherwise familiar aircraft. One has become a single-carrier type in the United States after a rival shut down.
This article looks at twin-engine variants that stand out among US passenger operators in 2026, ordered from the largest US fleet to the smallest. Simple Flying has already covered the wider picture in its look at a Boeing and an Airbus passenger jet that only three airlines still fly, and InsideFlyer has also highlighted three rare jets still flown by only three airlines. Here, the focus is on how many examples remain with US airlines, rather than how unusual each aircraft is worldwide.
6 Boeing 717
Delta Air Lines and Hawaiian Airlines
The Boeing 717 is the last member of the McDonnell Douglas DC-9 family, and in the United States it survives with just two carriers. 
Delta Air Lines still has about 80, which makes it the dominant operator by a wide margin, but that number is no longer stable. As the leak covered by View from the Wing suggests, Delta's Boeing 717 retirements are starting, with some jets being retired as they come due for heavy maintenance. The same report points to the possibility of a new Airbus or Boeing order down the road.
There is already a visible sign of change. InsideFlyer reported that Delta ended Boeing 717 flights from Minneapolis, with the final service operating in May 2026. For a type that long served Delta's northern network, that departure marks the beginning of a slow wind-down rather than a sudden exit. The other US operator is Hawaiian Airlines, which flies about 19 of them on interisland routes. Together, that is about 99 jets, the largest fleet on this list. AeroCorner has noted that Hawaiian Airlines will retire its Boeing 717s and begin replacing them with 737-800s from 2028. So both US operators are on a retirement path, even if the timing differs. It is a familiar story for older fleets. Simple Flying has already covered a similar story in its piece on the aircraft that built Southwest Airlines, which will be retired by 2031, a reminder that even iconic workhorses eventually reach the end of the line.
With about 99 aircraft still operated by US airlines, the 717 has the largest fleet among the six types featured here. It is not in danger of vanishing tomorrow, but as maintenance bills come due, the window to fly the last DC-9 relative is closing.
5 Airbus A320neo
Frontier Airlines
The Airbus A320neo is next, with 72 jets in Frontier's fleet as of June 30. The Airbus A320neo is hardly unusual around the world, but in the United States, it has become a single-operator aircraft. With Spirit Airlines' shutdown on May 2, 2026, Frontier Airlines became the only US airline flying the standard A320neo.
That status comes with an irony: Frontier is shrinking the fleet anyway. In March, the airline ended leases on 24 A320neos early and pushed back 69 future deliveries. As DWU Consulting explains in its look at Frontier Airlines' strategy and competitive position, the carrier has been reshaping its plans in a tough competitive environment. By June 30, Frontier flew 72 A320neos alongside 66 of the larger A321neos. Then, in August, it agreed to return 13 more A320neos early, this time to lessor Carlyle.
For context on why these jets move around so much, Simple Flying has already covered how much the Airbus A320neo costs in 2026, a useful reference for understanding why lessors and airlines continually juggle these assets. The A320neo isn't rare in global production numbers, but it's become less common on US fleet lists. As Frontier trims its fleet and leans more heavily on the larger A321neo, the smaller sibling could become even harder to find.
4 Boeing 757-300
Delta Air Lines and United Airlines
The longest narrowbody
Boeingever built is now a purely American affair too. Its 37 active jets put it level with the Boeing 767-400ER in this ranking. Delta and 
United Airlines fly all 37 active 757-300s on busy US routes since Condor and Icelandair stopped flying the type. In other words, any other operator in the world has left the stage, and the two US giants carry the torch.
United has the larger fleet, with 21 jets, while Delta has 16. Both airlines use them from major hubs such as 
Hartsfield-Jackson Atlanta International Airport(ATL), 
Chicago O'Hare International Airport(ORD), and 
Denver International Airport(DEN), and they point them toward big leisure markets like Orlando and Las Vegas. The logic is simple: these are dense, high-demand routes where a large single-aisle jet with a lot of seats makes sense. Few modern narrowbodies can match the 757-300's capacity, and even fewer share its distinctive, stretched silhouette.
The type is a favorite among aviation enthusiasts for another reason too. Passengers booking popular leisure routes from those hubs have a real chance of landing on one without trying. Still, the production run was small, the airframes are aging, and no new -300s will ever be built. That makes every flight a small piece of history, even with the type tied with the 767-400ER for fleet size among US operators.
3 Boeing 767-400ER
Delta Air Lines and United Airlines
With 37 active examples in US passenger service, the Boeing 767-400ER matches the 757-300 in fleet size, though it is rare globally and nearly all surviving passenger aircraft are in American hands. Boeing built only 38, and 37 still fly passengers. As Simple Flying explained in its guide to Delta Air Lines and United Airlines, the Boeing 767-400ER has only two airline customers left. Delta has 21, and United has 16.
United deploys its -400ERs primarily from Newark and Washington Dulles. Simple Flying has already covered how to catch United's rarest widebody from its two hubs, and the routes tend to fall into two groups. The first is transatlantic flying, mostly to Europe and including 
London Heathrow Airport(LHR). The second is busy domestic service to Honolulu, where the jet's high capacity suits heavy leisure demand.
The clock is ticking, at least for United. The airline plans to retire its entire 767 fleet by 2030. That timeline matters for enthusiasts because the -400ER is a stretched, long-fuselage variant with a distinctive profile, and no replacement is in sight that looks anything like it. Delta has not announced the same schedule in the source material, but the aircraft's age and the shrinking pool of operators make the long-term outlook clear. If you have a bucket list that includes this jet, do not wait too long.
2 Boeing 737 MAX 8-200
Allegiant Air
Not every uncommon aircraft is old. The Boeing 737 MAX 8-200 is a high-density version of the MAX 8, strongly associated with European ULCC Ryanair, but in the United States it belongs entirely to Allegiant Air. As Airways Magazine reported when Allegiant took delivery of the Boeing 737-8-200, the airline became the first US carrier to fly the type. ch-aviation also noted that Allegiant added its first B737 MAX 8-200, with the first aircraft arriving on September 9, 2024. Allegiant remains the only US operator.
The jet seats 190 passengers in a single cabin, including 21 "Allegiant Extra" seats with more legroom. That setup suits an ultra-low-cost, leisure-focused carrier perfectly: lots of seats, one class of service, and a premium-ish upsell for passengers who want a little more space.
The fleet is growing quickly. Allegiant flew 16 at the start of 2026 and planned to put nine more into service by year-end. According to Aviation Week, Allegiant is mulling timing for its MAX options while expecting Sun Country progress, and the planned purchase of Sun Country would make the combined airline mostly Boeing.
That is a big shift. Simple Flying has already covered how Allegiant is shifting from an all-Airbus fleet to a Boeing-first fleet, noting the change for an airline that has flown only Airbus jets since 2018. The MAX 8-200 remains uncommon in US skies, though that could change as Allegiant expands its fleet. For now, passengers boarding an Allegiant flight ride in a type no other US airline operates.
1 Boeing 737-900
United Airlines
The Boeing 737-900 without the extended-range upgrade is the rarest type on this list, and one most travelers will never notice. The Boeing 737-900 without the extended-range upgrade has just one US operator – United Airlines, after 
Alaska Airlines retired this type in 2025. According to The Blue Board's United Airlines fleet database, the carrier flies only 12 of them, each configured with 179 seats.
At the bottom of the list, the standard 737-900 is by far the least numerous type covered here. United operates a much larger fleet of 737-900ERs, the later version that sold in far greater numbers. To the casual observer, the two look nearly identical, which means the standard 737-900 is easy to fly on without ever realizing it. If you want to spot one, the best approach is to check the aircraft type on your booking and look at the seat count, since the 179-seat layout is a useful clue.
The original 737-900 was never a commercial hit. It was stretched to carry more passengers than the 737-800, but it lacked the extra exit doors and range of the ER version that followed. Airlines that wanted the size mostly waited for the improved model, leaving the base version a niche product. That niche is why United's dozen jets make this the rarest entry here: no other US airline has any.