82% of flights from Seattle to Chicago arrived on time over the past 12 months. That is better than the typical U.S. route. The 6 a.m. departures ran on time 94% of the time; the 11 p.m. ones 74%. 4% 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 SEA → MDW: when a flight was late, it was under 45 minutes late 70% of the time. About 1 in 36 flights landed an hour or more late; 0.4% were cancelled outright.
- On time or early82%
- 15–30 min late8.3%
- 30–60 min late5.9%
- 1–2 hours late2.4%
- 2–3 hours late0.3%
- 3+ hours late0.1%
- Diverted0.6%
- Cancelled0.4%
Share of all 678 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 |
|---|---|---|---|---|---|---|---|
| Southwest Airlines | 678 | 82% | 0.4% | −6 min | 2.8% | +42 min | Southwest Airlines |
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 SEA). Delays build through the day as late planes knock on, so early flights usually do best.
Last flight of the day
On SEA → MDW, each airline's last flight of the day was cancelled 0.0% of the time, against 1.0% for its earlier flights, so here the last flight is actually the safer one. It arrived 3+ hours late 0.0% of the time (earlier flights: 0.3%). 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 |
|---|---|---|---|---|---|
| Southwest Airlines | 11:05 p.m. | 0.0% | 0.0% | 1.0% | first flight 5:25 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.
By month
Each calendar month pooled over 2023–2026. Best: March (93%). Worst: July (67%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 102 | 81% | 1.0% |
| Tuesday | 99 | — | — |
| Wednesday | 99 | — | — |
| Thursday | 99 | — | — |
| Friday | 99 | — | — |
| Saturday | 90 | — | — |
| Sunday | 90 | — | — |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 2 · air traffic/airport 1
Month by month
Not enough months with data to draw a trend.
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Jun 9, 2026 | 3 | 0% | 0 |
| Sep 19, 2025 | 3 | 0% | 0 |
| Jun 11, 2026 | 3 | 33% | 0 |
| Jul 7, 2026 | 3 | 33% | 0 |
| Sep 11, 2025 | 3 | 33% | 0 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of Seattle or Chicago. None has been clearly more reliable than SEA → MDW.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| SEA → MDW (this route) | 678 | 82% | 0.4% |
| SEA → ORD Seattle-Tacoma to Chicago O'Hare | 5,538 | 75% | 1.2% |
Questions
How often are flights from SEA to MDW on time?
82% of 678 scheduled flights from Seattle, WA to Chicago, IL 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 SEA to MDW?
Flights scheduled to leave at 6 a.m. were the most reliable (94% on time). The 11 p.m. departures were the least (74%).
What month has the most delays from SEA to MDW?
July (67% on time). The best month is March (93%), over 2023–2026.
Is the last flight of the day from SEA to MDW more likely to be cancelled?
No, the opposite. Each airline's last SEA–MDW flight of the day was cancelled 0.0% of the time over the past year, against 1.0% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- MDW → SEA (return)
- Seattle-Tacoma (SEA) delays by hour
- Flights into Chicago Midway (MDW)
- Southwest 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.