ATIS Alerts Smart Flight Search
Find the flight least likely to be delayed
BetaWe rank real flight numbers by how often they flew and arrived on time over the last 12 months, adjusted for your travel month and departure time, then check nearby airports and calmer connections. US airlines and airports.
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%).
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