Look at the departures board at Aspen-Pitkin County Airport (airport codes KASE and ASE), and you'll see something unusual. Almost every commercial flight is the same plane: the Embraer E-175. The only exception is a handful of American Eagle flights on the Bombardier CRJ-700. No 737s. No A320s. Not even a slightly bigger plane like the E-190. This isn't a scheduling choice by the airlines. It's a hard physical rule built into the runway itself.
The Short Answer: A 95-Foot Wingspan Rule
Aspen's airport has a strict 95-foot wingspan limit. Wingspan is the distance from one wingtip to the other. Any plane wider than 95 feet is not allowed to land or take off there, no matter how skilled the pilot is or how nice the weather is. The E-175 has a wingspan of about 93 feet 11 inches; just barely under the limit. The CRJ-700 is much smaller at about 76 feet 3 inches. Almost every full-sized jet you'd see at a normal airport is wider than 95 feet, which is why they can't fly to Aspen.
There's also a weight limit: 100,000 pounds at takeoff. The runway pavement can't safely hold heavier planes. Both the E-175 and CRJ-700 are well under that limit. A Boeing 737-700 weighs closer to 154,500 pounds at takeoff. So even if its wings somehow fit, the runway couldn't hold it.
Why a 95-Foot Wingspan? It Comes Down to Runway Design
The wingspan rule isn't really about the mountains or the thin mountain air. It's about how the runway and the taxiway are spaced. A taxiway is the smaller paved path that planes use to drive between the gate and the runway. At most commercial airports, the FAA (the federal agency that sets U.S. aviation rules) requires at least 400 feet between the center of the runway and the center of the taxiway. That gap is what lets one plane taxi past safely while another plane is taking off or landing.
Aspen's runway and taxiway are only 320 feet apart. That's a smaller gap than current FAA standards allow for planes Aspen's size. The airport was built into a tight valley decades ago. There simply isn't room to move the taxiway farther away from the runway without major construction and buying more land.
In 1999, the FAA agreed to let Aspen keep its narrower setup as a special exception. But the exception came with a rule: Pitkin County had to agree to cap all aircraft wingspans at 95 feet. The smaller wings keep a safe buffer between a plane on the runway and a plane on the taxiway. That cap has been in place ever since.
In short: the 95-foot rule exists because the runway and taxiway are too close together for FAA standards. Limiting the size of planes was the trade-off that kept Aspen open to commercial flights.
Which Aircraft Fit (and Which Don't)
Here's how common commercial aircraft stack up against Aspen's 95-foot wingspan limit:
| Aircraft | Wingspan | Seats (typical) | Operates at ASE? |
|---|---|---|---|
| Bombardier CRJ-700 | ~76 ft 3 in | ~65–70 | Yes (American Eagle) |
| Embraer E-175 | ~93 ft 11 in | ~70–78 | Yes (United Express, Delta Connection) |
| Airbus A220-100 | ~115 ft 1 in | ~110–135 | No, too wide |
| Embraer E-190 / E-195-E2 | ~94–110 ft | ~96–146 | No, too wide (E2 variants) |
| Airbus A319 / A320 | ~111 ft 11 in | ~124–180 | No, too wide and too heavy |
| Boeing 737-700 (with winglets) | ~117 ft 5 in | ~124–149 | No, too wide and too heavy |
| Boeing 737 MAX 8 | ~117 ft 10 in | ~162–200 | No, too wide and too heavy |
Once you see the numbers, the answer is pretty clear. Almost every modern full-sized jet is too wide for Aspen. The E-175 fits with just an inch or two to spare, which is why airlines use it for most Aspen flights. The CRJ-700 is smaller and fits easily, but it carries fewer passengers. Airlines pick the E-175 whenever they can, simply because it can seat more people per flight.
The Embraer E-175
SkyWest Airlines flies the E-175 into Aspen under two airline brands. The first is United Express, with flights to United hubs including Denver, Houston, Chicago, San Francisco, and Los Angeles. The second is Delta Connection, on select routes to Delta hubs. The E-175 is a two-engine regional jet with two seats on each side of the aisle. It's built for the kind of mid-sized routes that don't need a bigger plane like a 737. Its 93' 11" wingspan also makes it one of the only modern regional jets that fits Aspen's limit without any special design changes.
The Bombardier CRJ-700
The CRJ-700 is the smaller of the two planes. SkyWest also flies it into Aspen, under the American Eagle brand, on routes from American hubs including Dallas/Fort Worth, Chicago, and Los Angeles. It's an older plane with a tighter cabin and less shoulder room than the E-175. But its small 76-foot wingspan and lower weight make it a good fit for airports like Aspen. The CRJ-700 also has slightly stricter limits for crosswinds and approach conditions than the E-175. That's part of why American flights sometimes cancel even when United and Delta are still flying. We covered the weather angle in detail in our breakdown of weather-driven Aspen delays.
It's Not Just the Wingspan Rule
The 95-foot rule is the biggest reason, but it's not the only one. A few other physical facts also explain why only small regional jets can fly to Aspen:
- High elevation (7,820 feet above sea level): Aspen sits high in the mountains. The air is thinner up there. Thinner air means less thrust from the engines and less lift on the wings. So planes need a longer runway to take off and have to carry less weight. Bigger jets would have a hard time leaving Aspen with a full load of passengers and fuel, even if the wingspan rule didn't exist.
- One runway, 8,006 feet long (called Runway 15/33): There's only one runway, and it's just over 8,000 feet long. That's long enough for regional jets but short for bigger planes, especially when the high altitude is making takeoffs harder. The runway also slopes uphill about 2% toward the southeast.
- Mountains on every side, and no precision landing system: Aspen is surrounded by peaks over 14,000 feet tall. Most major airports have a precision landing system that guides planes down in bad weather. Aspen doesn't. Pilots flying in have to use a steeper approach and need clearer weather than at a regular airport. That's part of why Aspen sees so many weather-driven delays and diversions.
- Steep climb requirements after takeoff: Planes must climb steeply after takeoff to clear the surrounding mountains. Smaller, lighter planes can do this far more easily than larger, fully-loaded jets.
Why Aspen Doesn't Just Use the E-190 or A220 Instead
Some travelers ask why airlines don't fly slightly larger regional jets like the Embraer E-190 or Airbus A220 to Aspen. The answer is the wingspan rule. The E-190-E2 has a wingspan of about 110 feet, and the A220-100 is 115 feet 1 inch. Both are too wide. Until the runway and taxiway are moved farther apart, these planes can't be added to the Aspen route map, even though they're popular at other airports.
What's Changing: The ASE Modernization Project
The 95-foot wingspan rule isn't going to last forever. In November 2024, Pitkin County voters approved a major Airport Modernization Project. It will rebuild the airfield to today's FAA standards and replace the old terminal. The project is one of the biggest infrastructure investments in the region's history. The estimated cost is roughly $575 million, with construction phases running through 2029.
The big changes that affect aircraft restrictions:
- Runway shifted 80 feet to the west. This widens the gap between the runway and the taxiway enough to meet today's FAA standards. That's what makes it possible to remove the 95-foot wingspan cap.
- Runway widened from 100 feet to 150 feet. This brings the runway itself up to the standard width for the size of planes the airport is designed to handle.
- A new passenger terminal. The current terminal has been at capacity for years. It will be replaced with a modern one built for today's and tomorrow's traffic.
- More aircraft options in the future. Once the airfield is rebuilt, larger and more modern planes could be approved to fly at Aspen. Examples include the Embraer E-2 family, the A220, and other types with wider wings.
The project is in its design phase right now. ZGF Architects is designing the terminal, and Kimley-Horn is designing the runway. Some prep work is scheduled to begin in summer 2026. This includes moving Owl Creek Road, relocating the bike path next to it, and updating certain utilities. The main runway construction is planned for one long closure during the 2027 construction season (roughly April through November 2027). The new terminal is targeted to open in 2029, when the old terminal will be torn down.
For now, though, the 95-foot rule is still in place. The E-175 and CRJ-700 remain the only aircraft you'll see flying scheduled service into Aspen.
The Bottom Line
The reason every flight to Aspen looks the same isn't a marketing choice. It's a direct result of how the runway and taxiway are spaced, set in a 1999 FAA agreement. The 95-foot wingspan cap makes Aspen one of the only commercial airports in the country limited to just two types of aircraft. The modernization project will change that eventually. But until at least 2028 or 2029, your flight to Aspen will almost certainly be on an E-175. Less often, it might be on a CRJ-700.
Both planes have specific safety limits for visibility, cloud height, and wind. That means weather has a big effect on whether they can safely fly into Aspen. The KASE Weather dashboard tracks these conditions in real time and scores them against the actual limits these planes fly to. If you want a heads-up when conditions are moving toward delays or diversions, KASE Weather Premium can alert you by email before the airline does.