Route on-time record
SEA to MDW: most on-time flights and the best time to fly
Seattle (Seattle–Tacoma International Airport) to Chicago (Chicago Midway International Airport). 673 nonstop flights in Jun 2025 to May 2026, 81% arrived within 15 minutes and 0.4% were cancelled. The most reliable flight number was Southwest 1807 at 5:15 AM.
Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.
SEA → MDW
Seattle to Chicago: 673 nonstop flights a year
On time (12 months)
81%
Cancelled
0.4%
avg delay 9 min
Best time to leave
Before 9 AM
92% on time vs 39% noon to 3 PM
Most reliable airline
Southwest
81% chance on time
Lowest nonstop fare seen in the next two months: $142 (Southwest 4975 on 2026-11-10). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.
Most reliable nonstop flights
Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.
#1 · Southwest 1807
5:15 AM → 11:10 AM3h 55m nonstop
Local times, typical schedule. Last flown 2026-05-31.
91%
chance on time
- On time (history)
- 95%
- Cancelled
- 0.0%
- Avg arrival delay
- 4 min
- Arrived on time 95% of the time (55 flights, Jun 2025 to May 2026).
- Never cancelled in 55 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 92% on time; Noon to 3 PM: 39%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Limited track record · 55 flights
Find Southwest 1807 fares Opens this date on Aviasales#2 · Southwest 2123
5:30 AM → 11:20 AM3h 55m nonstop
Local times, typical schedule. Last flown 2026-04-06.
88%
chance on time
- On time (history)
- 94%
- Cancelled
- 6.1%
- Avg arrival delay
- 4 min
- Arrived on time 94% of the time (31 flights, Jun 2025 to May 2026).
- Cancelled 6.1% of the time (2 of 33).
- Leaves in this route's most on-time window (Before 9 AM: 92% on time; Noon to 3 PM: 39%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Limited track record · 31 flights
Find Southwest 2123 fares Opens this date on Aviasales#3 · Southwest 4198
11:55 PM → 5:55 AM4h 00m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Southwest 4419; its record covers all of them.
81%
chance on time
- On time (history)
- 84%
- Cancelled
- 0.0%
- Avg arrival delay
- 7 min
- Arrived on time 84% of the time (70 flights, Jun 2025 to May 2026).
- Never cancelled in 70 scheduled flights.
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Moderate track record · 70 flights
Find Southwest 4198 fares Opens this date on Aviasales#4 · Southwest 3951
11:45 PM → 5:45 AM4h 00m nonstop
Local times, typical schedule. Last flown 2026-05-27.
77%
chance on time
- On time (history)
- 69%
- Cancelled
- 0.0%
- Avg arrival delay
- 8 min
- Arrived on time 69% of the time (16 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (16 flights), so its score leans on the airline's record at this hour.
Limited track record · 16 flights
Find Southwest 3951 fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- Southwest Airlines81%
673 flights · 81% on time as flown · 0.4% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM92%
350 flights · avg delay 4 min
- 9 AM to noon74%
40 flights · avg delay 15 min
- Noon to 3 PM39%
76 flights · avg delay 25 min
- After 9 PM78%
207 flights · avg delay 9 min
Best day: Tuesday (83%). Worst: Thursday (74%).
On time by month
All airlines, Jun 2023 to May 2026. Several years per month, so one stormy season doesn't define a month. Travel-month estimates use this seasonal pattern.
What delays this route
- Late-arriving aircraft47%
- Airline (crew, maintenance, boarding)36%
- Air traffic control and airport volume15%
- Security1%
Share of delay minutes by the cause airlines report to the US DOT.
Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure
SEA to MDW questions
- What time of day is best to fly SEA to MDW?
- Before 9 AM: 92% of flights arrived on time, against 39% for departures noon to 3 PM. Later flights inherit delays from earlier ones, so the first departures of the day usually run best.
- Which airline is most on time from SEA to MDW?
- Southwest, with a season-adjusted 81% chance of operating and arriving on time over 673 flights. The adjustment compares each airline with what the route did in the months it flew, so a carrier that skipped a stormy month gets no free credit.
- What is the worst month for delays on SEA to MDW?
- July (65% on time); the best was March (95%), averaged over Jun 2023 to May 2026.
- Is this a prediction for my flight?
- No. These are historical odds from the US DOT on-time reports, FAA advisories and airport weather records. Check your flight status and the FAA delay board on the day you fly.
More routes from SEA
- MDW to SEA (return)
- SEA to LAX 83%
- SEA to PHX 79%
- SEA to SFO 69%
- SEA to ANC 74%
- SEA to DEN 77%
- SEA to LAS 77%
- SEA to ORD 75%
- SEA to GEG 81%
- SEA to DFW 77%
- SEA to PDX 82%
- SEA to SAN 78%
- SEA to SMF 81%
Live status: FAA delays and ground stops