79% of flights from Chicago to Missoula arrived on time over the past 12 months. That is about the typical U.S. route. The 8 a.m. departures ran on time 86% of the time; the 9 a.m. ones 76%. Most reliable airline: United Airlines (84%). 7% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for ORD → MSO: when a flight was late, it was under 45 minutes late 62% of the time. About 1 in 18 flights landed an hour or more late, and 1 in 236 three hours or more; 0.4% were cancelled outright.
- On time or early79%
- 15–30 min late7.6%
- 30–60 min late6.6%
- 1–2 hours late4.2%
- 2–3 hours late0.8%
- 3+ hours late0.4%
- Diverted0.6%
- Cancelled0.4%
Share of all 472 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| American Airlines | 315 | 77% | 0.0% | −5 min | 6.0% | +50 min | Envoy |
| United Airlines | 157 | 84% | 1.3% | −9 min | 4.5% | +60 min | United Airlines 53%, SkyWest 47% |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at ORD). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | American Airlines | United Airlines |
|---|---|---|
| 8 a.m. | — | 86% |
| 9 a.m. | 76% | — |
By month
Each calendar month pooled over 2023–2026. Best: September (87%). Worst: August (76%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 71 | — | — |
| Tuesday | 65 | — | — |
| Wednesday | 65 | — | — |
| Thursday | 71 | — | — |
| Friday | 67 | — | — |
| Saturday | 67 | — | — |
| Sunday | 66 | — | — |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 2
Month by month
Not enough months with data to draw a trend.
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Sep 13, 2025 | 3 | 33% | 1 |
| Sep 29, 2025 | 3 | 67% | 0 |
| Jul 30, 2026 | 3 | 67% | 0 |
| Jul 16, 2026 | 3 | 67% | 0 |
| Sep 28, 2025 | 3 | 67% | 0 |
Questions
How often are flights from ORD to MSO on time?
79% of 472 scheduled flights from Chicago, IL to Missoula, MT arrived within 15 minutes of schedule between September 2025 and August 2026. 0.4% were cancelled.
What is the best time of day to fly ORD to MSO?
Flights scheduled to leave at 8 a.m. were the most reliable (86% on time). The 9 a.m. departures were the least (76%).
Which airline is most on time from ORD to MSO?
United Airlines: 84% of its 157 flights on the route arrived on time. American Airlines: 77%.
What month has the most delays from ORD to MSO?
August (76% on time). The best month is September (87%), over 2023–2026.
Related
- MSO → ORD (return)
- Chicago O'Hare (ORD) delays by hour
- Flights into Missoula Montana (MSO)
- American Airlines on-time record
- United Airlines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.