75% of flights from Portland to Chicago arrived on time over the past 12 months. That is worse than the typical U.S. route. The 6 a.m. departures ran on time 89% of the time; the 5 p.m. ones 56%. Most reliable airline: American Airlines (75%). 12% 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 PWM → ORD: when a flight was late, it was under 45 minutes late 53% of the time. About 1 in 13 flights landed an hour or more late, and 1 in 38 three hours or more; 3.4% were cancelled outright.
- On time or early75%
- 15–30 min late8.2%
- 30–60 min late5.2%
- 1–2 hours late3.4%
- 2–3 hours late1.8%
- 3+ hours late2.6%
- Diverted0.4%
- Cancelled3.4%
Share of all 1,493 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 |
|---|---|---|---|---|---|---|---|
| United Airlines | 812 | 75% | 2.7% | −4 min | 7.4% | +84 min | United Airlines 53%, Republic Airways 25%, SkyWest 22% |
| American Airlines | 681 | 75% | 4.3% | −9 min | 8.4% | +92 min | Republic Airways 59%, Envoy 29%, SkyWest 11%, American Airlines 1% |
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 PWM). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | United Airlines | American Airlines |
|---|---|---|
| 6 a.m. | 94% | 82% |
| noon | — | 81% |
| 4 p.m. | 65% | — |
| 5 p.m. | 51% | — |
Last flight of the day
On PWM → ORD, each airline's last flight of the day was cancelled 4.5% of the time, against 2.3% for its earlier flights (2.0× as often). It arrived 3+ hours late 3.7% of the time (earlier flights: 1.7%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| American Airlines | 7:28 p.m. | 6.7% | 2.9% | 2.1% | first flight 6:09 a.m. |
| United Airlines | 5:00 p.m. | 2.8% | 4.3% | 2.5% | first flight 6:00 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
If you need to be in ORD tonight, book an earlier flight so there's a backup if it's cancelled.
By month
Each calendar month pooled over 2023–2026. Best: May (87%). Worst: August (71%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 222 | 73% | 8.6% |
| Tuesday | 208 | 75% | 1.4% |
| Wednesday | 205 | 74% | 1.0% |
| Thursday | 215 | 77% | 3.3% |
| Friday | 218 | 77% | 2.8% |
| Saturday | 209 | 74% | 4.3% |
| Sunday | 216 | 76% | 2.3% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 29 · air traffic/airport 17 · airline 5
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| AA 4391 | 6:00 a.m. | 135 | 81% | 3.0% | −10 min | Republic Airways |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Nov 10, 2025 | 3 | 0% | 2 |
| Nov 29, 2025 | 3 | 0% | 3 |
| Feb 23, 2026 | 3 | 0% | 3 |
| Nov 30, 2025 | 3 | 0% | 1 |
| Nov 9, 2025 | 3 | 0% | 1 |
Questions
How often are flights from PWM to ORD on time?
75% of 1,493 scheduled flights from Portland, ME to Chicago, IL arrived within 15 minutes of schedule between September 2025 and August 2026. 3.4% were cancelled.
What is the best time of day to fly PWM to ORD?
Flights scheduled to leave at 6 a.m. were the most reliable (89% on time). The 5 p.m. departures were the least (56%).
Which airline is most on time from PWM to ORD?
American Airlines: 75% of its 681 flights on the route arrived on time. United Airlines: 75%.
What month has the most delays from PWM to ORD?
August (71% on time). The best month is May (87%), over 2023–2026.
Is the last flight of the day from PWM to ORD more likely to be cancelled?
Yes. Each airline's last PWM–ORD flight of the day was cancelled 4.5% of the time over the past year, against 2.3% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- ORD → PWM (return)
- Portland Jetport (PWM) delays by hour
- Flights into Chicago O'Hare (ORD)
- United Airlines on-time record
- American 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.