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 a Stacker analysis of BTS on-time performance data covering August 2021 through July 2022.
| Metric | ASE (Aug 2021–Jul 2022, BTS) | National Avg. |
|---|---|---|
| On-time arrival rate | ~59% | ~78% |
| Cancellation rate | 8.2% | ~1.5% |
| Diversion rate | ~3% | ~0.2% |
| Annual scheduled flights | ~6,500 | – |
Sources: Stacker analysis of Bureau of Transportation Statistics (BTS) on-time performance data, August 2021 through July 2022; Aspen/Pitkin County Airport operational reports; Fly Aspen Snowmass / Air Planners consultant data.
One caution before you read too much into this table: it covers a COVID-recovery stretch when airline schedules were still unsettled, so it shows ASE near its worst. Recent years have run much better, as the completion-rate sections below show.
The headline: in that period, ASE flights were delayed more often than at most U.S. airports. A Stacker analysis of BTS data for August 2021 through July 2022 ranked Aspen among the top airports nationally for delay frequency. The cancellation rate of 8.2% was more than five times the national average, and the diversion rate, meaning flights forced to land somewhere other than Aspen, typically Grand Junction (GJT), was about 15 times higher than the national norm.
What makes ASE unique is why flights are disrupted. According to BTS delay cause data for that same August 2021 to July 2022 window, air carrier factors (scheduling, crew, maintenance) delayed about 19.1% of all flights, late-arriving aircraft delayed 7.2%, weather delayed 1.8%, and the National Airspace System delayed 1.7%. That weather figure may look small, but it's misleading: Aspen's winter weather patterns often trigger the cascading carrier 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 | 88–92% | 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 2025 dipped to 94.4% avg (Jun–Aug) |
| July | 94–97% | Moderate | Afternoon thunderstorms; wind policy changes impacted 2025 |
| August | 94–97% | Moderate | Monsoon moisture; gusty afternoon winds |
| September | 99–100% | Very Low | Sep 2025: 99.8% completion |
| October | 99–100% | Very Low | Oct 2025: 100%, "very rare" per Bill Tomcich of Fly Aspen Snowmass |
| 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; 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. For the weather-side explanation of why these patterns hold, see why Aspen flights get delayed.
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
- December 2025: the holiday period (Dec 17–29) ran at 96%, with 466 of 487 inbound 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, on December 27 alone, 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 220 miles east by road. 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. If it happens to you, here's how to rebook after an Aspen diversion.
- Colorado Springs (COS): Occasionally used as a fuel stop, with flights continuing to Aspen once conditions improve.
What Causes That Outbound vs. Inbound Gap?
Over a recent multi-year window of BTS data, Aspen's outbound cancellation rate (about 6.5%) ran notably higher than its inbound rate (about 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. Private operators dodge much of this cascade because they fly point-to-point and don't share aircraft across a turn schedule. See flying private vs. commercial to Aspen for how the weather risk profile differs.
Summer Completion Rate Trends (June–August)
Summer gives the cleanest year-to-year comparison, because the schedule and weather are most consistent. These figures are June through August averages for each year, not full-year rates. They held remarkably steady until 2025:
| Year | Summer Completion Rate (Jun–Aug) | Total Passengers (Full Year) | Notes |
|---|---|---|---|
| 2022 | 97.7% | – | Steady summer performance |
| 2023 | 98.3% | 627,919 | Record passengers; best recent summer |
| 2024 | 96.9% | 698,000 | Slight dip, still near the recent norm |
| 2025 | 94.4% | – | Rough summer after a wind-reporting change |
Sources: Aspen/Pitkin County Airport reports; BTS; Aspen Times reporting.
The 2025 dip was notable. June through August 2025 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 took effect before that summer and aligned with a higher rate of disruptions. After the rough summer, the airport recovered sharply in fall 2025, 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 2025 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. The same government flight records behind this page now train the dashboard's v2 delay prediction model.
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 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.