How likely is your flight to Aspen to actually land on time? It's the question every traveler asks, and the answer depends heavily on when you're flying. We pulled data from the U.S. Department of Transportation's Bureau of Transportation Statistics (BTS) and supplemented it with operational reports from the Aspen/Pitkin County Airport to build a month-by-month picture of delays, diversions, and cancellations at ASE.
The Big Picture: ASE by the Numbers
Before diving into monthly trends, here's how Aspen-Pitkin County Airport stacks up overall. These figures come from BTS on-time performance data.
| Metric | ASE (2024) | National Avg. |
|---|---|---|
| On-time arrival rate | ~59% | ~78% |
| Average delay (when delayed) | 26 minutes | ~56 minutes |
| Cancellation rate | 5.4% | ~1.5% |
| Diversion rate | ~3% | ~0.2% |
| Annual scheduled flights | ~6,500 | — |
Sources: Bureau of Transportation Statistics (BTS) on-time performance data; Aspen/Pitkin County Airport operational reports; Fly Aspen Snowmass / Air Planners consultant data.
The headline: ASE flights are delayed more often than at most U.S. airports, but when delays happen, they tend to be shorter on average. BTS data ranks Aspen among the top airports nationally for delay frequency. The cancellation rate of roughly 5.4% is more than three times the national average, and the diversion rate — flights forced to land somewhere other than Aspen, typically Grand Junction (GJT) — is about 15 times higher than the national norm.
What makes ASE unique is why flights are disrupted. According to BTS delay cause data, air carrier factors (scheduling, crew, maintenance) account for 19.1% of delays, late-arriving aircraft for 7.2%, weather for 1.8%, and the National Airspace System for 1.7%. That weather figure may look small, but it's misleading: weather at Aspen often triggers the cascading carrier and NAS delays that show up in other categories. When a morning storm blocks inbound flights, every subsequent departure that day is affected by the late-arriving aircraft.
Flight Completion Rates by Month
Flight completion rate — the percentage of scheduled flights that actually operated without being canceled or diverted — is the metric that matters most to travelers. Here's how it breaks down across the year, drawn from airport operational data and BTS records for 2022–2025.
| Month | Typical Completion Rate | Risk Level | Notes |
|---|---|---|---|
| January | 90–94% | High | Peak ski season; heavy snow, low ceilings frequent |
| February | 89–92% | High | Historically worst month; Feb 2023: 88.9%, Feb 2024: 92% |
| March | 92–96% | Moderate-High | Still heavy traffic; spring storms can close airport |
| April | 95–98% | Moderate | Shoulder season; fewer flights, variable weather |
| May | 97–99% | Low | Mud season; minimal traffic, generally clear skies |
| June | 94–97% | Moderate | Summer 2024 dipped to 94.4% avg (Jun–Aug) |
| July | 94–97% | Moderate | Afternoon thunderstorms; wind policy changes impacted 2024 |
| August | 94–97% | Moderate | Monsoon moisture; gusty afternoon winds |
| September | 99–100% | Very Low | Sep 2024: 99.8% completion |
| October | 99–100% | Very Low | Oct 2024: 100% — "very rare" per analysts |
| November | 96–99% | Low | Light schedule; early-season storms possible |
| December | 88–96% | High | Wide range: Dec 2022: 88.7%, Dec 2023: 95.8%, Dec 2024: 91% |
Sources: Aspen/Pitkin County Airport operational data (via Bill Tomcich / Air Planners); BTS on-time performance database; Aspen Times and Aspen Daily News reporting (2022–2025). Ranges reflect year-to-year variation.
The pattern is clear: September and October are the safest months to fly into Aspen, with near-perfect completion rates. February and December are the riskiest, with one in ten flights potentially canceled or diverted in a bad year.
December: The Wildcard Month
December deserves special attention because it combines the worst weather conditions with the heaviest holiday traffic. The data swings dramatically year to year:
- December 2022: 88.7% completion — one of the worst months on record, with storm systems stacking up over the holidays
- December 2023: 95.8% completion — a dramatically better year, with nearly two full weeks over the holidays without a single commercial cancellation
- December 2024: 91% completion for the full month, though the holiday period (Dec 17–29) performed better at 96% (466 of 487 flights completed)
Even during that relatively smooth December 2025–26 holiday period, a single heavy snowfall event on December 27–28 (9 inches overnight) caused 3 diversions to Grand Junction, 1 diversion to Denver, 4 inbound cancellations, 8 outbound cancellations, and 23 outbound delays exceeding one hour. That's a vivid example of how quickly conditions can deteriorate at ASE.
Where Do Diverted Flights Go?
When a flight can't land at Aspen, it doesn't just circle endlessly. The aircraft serving ASE — primarily the Embraer E175 and CRJ-700 — have limited fuel range, and the circling approach in mountain terrain burns fuel quickly. The most common diversion destinations are:
- Grand Junction (GJT) — About 130 miles west, this is the most common diversion airport. Airlines sometimes bus passengers the remaining distance to Aspen after a GJT diversion, though the drive takes roughly 2.5 hours on I-70 and Highway 82.
- Denver (DEN) — About 200 miles east. Flights are more likely to divert to Denver when the weather system is regional and Grand Junction is also affected, or when the airline can rebook passengers onto later flights.
- Colorado Springs (COS) — Occasionally used as a fuel stop, with flights continuing to Aspen once conditions improve.
What Causes That Outbound vs. Inbound Gap?
BTS data shows Aspen's outbound cancellation rate (6.5%) is notably higher than its inbound rate (4.3%). Why? When weather prevents inbound flights from arriving, the aircraft that was supposed to turn around for the outbound flight simply isn't there. One canceled inbound flight creates a cascade: the outbound departure gets canceled too, and if that aircraft was scheduled to return later, a second round of cancellations follows. This cascading effect is amplified at a single-runway, end-of-line airport like ASE where there are no spare aircraft on the ground.
Annual Completion Rate Trends
The airport has maintained a generally improving trend in overall annual flight completion, though individual months can still be volatile:
| Year | Annual Completion Rate | Total Passengers | Notes |
|---|---|---|---|
| 2022 | 97.7% | — | Rough December (88.7%) pulled down the average |
| 2023 | 98.3% | 627,919 | Record passengers; strong winter completion |
| 2024 | 96.9% | 698,000 | Summer wind-reporting changes impacted Jun–Aug |
Sources: Aspen/Pitkin County Airport reports; BTS; Aspen Times reporting.
The dip in 2024's annual rate was notable. The summer months of June through August averaged just 94.4% completion — more than 3 percentage points below the 97.5% average for those months over the preceding four years. Airport officials attributed this partly to an FAA policy change that shifted the control tower from reporting instantaneous wind speeds to average wind speeds, which aligned with a higher rate of disruptions. The airport recovered sharply in the fall, with September at 99.8% and October reaching a rare 100%.
How to Use This Data
If you're planning a trip to Aspen and have flexibility on dates, these numbers can guide your decisions:
- Lowest risk: September through November. Near-perfect completion rates and pleasant shoulder-season weather. If you're flexible on ski timing, late November offers early-season skiing with far fewer flight disruptions than December or February.
- Moderate risk: April through August. Spring and summer are generally reliable, though summer 2024 showed that afternoon thunderstorms and wind can still cause problems. Book morning flights for the best odds.
- Highest risk: December through March. This is when you most need a backup plan. Consider booking a flexible fare, arriving a day early for must-make events, and monitoring conditions in real time with KASE Weather.
No matter when you fly, checking real-time conditions before you leave for the airport is the single most useful thing you can do. The KASE Weather dashboard shows you the same visibility, ceiling, and wind data that pilots and dispatchers use, scored against the actual limits of the E175 and CRJ-700 aircraft that serve Aspen. If conditions are RED, there's a strong chance your flight won't make it in — and you'll know before the airline sends that notification.
Data Sources and Methodology
The statistics in this article are compiled from:
- Bureau of Transportation Statistics (BTS) — The U.S. DOT's official source for airline on-time performance, delay causes, cancellation rates, and diversion data. Airlines with at least 0.5% of domestic scheduled passenger revenue are required to report this data monthly. Available at transtats.bts.gov.
- Aspen/Pitkin County Airport operational reports — Published by the airport authority and available on their reports page.
- Air Planners / Fly Aspen Snowmass — Flight completion data compiled by aviation consultant Bill Tomcich, as reported in the Aspen Times and Aspen Daily News.
Completion rates may vary slightly between sources due to differences in how diversions, significant delays, and flight number changes are categorized. Where ranges are shown, they reflect observed year-to-year variation from 2022 through 2025.