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.
STL → MDW
St Louis to Chicago: 1,706 nonstop flights a year
On time (12 months)
81%
Cancelled
1.1%
avg delay 12 min
Best time to leave
Before 9 AM
92% on time vs 66% after 9 PM
Most reliable airline
Southwest
80% chance on time
Lowest nonstop fare seen in the next two months: $280 (Southwest 269 on 2026-10-23). 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 4489
5:40 AM → 6:50 AM1h 10m nonstop
Local times, typical schedule. Last flown 2026-05-31.
91%
chance on time
- On time (history)
- 95%
- Cancelled
- 0.0%
- Avg arrival delay
- 5 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; After 9 PM: 66%).
- Short track record (55 flights), so its score leans on the airline's record at this hour.
Limited track record · 55 flights
Find Southwest 4489 fares Opens this date on Aviasales#2 · Southwest 649
5:30 AM → 6:40 AM1h 10m nonstop
Local times, typical schedule. Last flown 2026-04-06.
89%
chance on time
- On time (history)
- 89%
- Cancelled
- 3.6%
- Avg arrival delay
- 12 min
- Arrived on time 89% of the time (27 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 92% on time; After 9 PM: 66%).
- Short track record (27 flights), so its score leans on the airline's record at this hour.
Limited track record · 27 flights
Find Southwest 649 fares Opens this date on Aviasales#3 · Southwest 397
7:20 AM → 8:30 AM1h 10m nonstop
Local times, typical schedule. Last flown 2026-05-29.
84%
chance on time
- On time (history)
- 91%
- Cancelled
- 4.3%
- Avg arrival delay
- 4 min
- Arrived on time 91% of the time (22 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 92% on time; After 9 PM: 66%).
- Lands inside MDW's trouble window: 50% of its 30 ground stops and delay programs started between 7 AM and 1 PM.
- Short track record (22 flights), so its score leans on the airline's record at this hour.
Limited track record · 22 flights
Find Southwest 397 fares Opens this date on Aviasales#4 · Southwest 2256
2:15 PM → 3:20 PM1h 05m nonstop
Local times, typical schedule. Last flown 2026-04-06.
84%
chance on time
- On time (history)
- 80%
- Cancelled
- 0.0%
- Avg arrival delay
- 22 min
- Arrived on time 80% of the time (15 flights, Jun 2025 to May 2026).
- Short track record (15 flights), so its score leans on the airline's record at this hour.
Limited track record · 15 flights
Find Southwest 2256 fares Opens this date on Aviasales#5 · Southwest 3613
10:50 AM → 12:00 PM1h 10m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Southwest 770; its record covers all of them.
84%
chance on time
- On time (history)
- 87%
- Cancelled
- 6.3%
- Avg arrival delay
- 12 min
- Arrived on time 87% of the time (60 flights, Jun 2025 to May 2026).
- Cancelled 6.3% of the time (4 of 64).
- Lands inside MDW's trouble window: 50% of its 30 ground stops and delay programs started between 7 AM and 1 PM.
Moderate track record · 60 flights
Find Southwest 3613 fares Opens this date on Aviasales#6 · Southwest 826
1:45 PM → 2:55 PM1h 10m nonstop
Local times, typical schedule. Last flown 2026-05-31.
82%
chance on time
- On time (history)
- 83%
- Cancelled
- 0.0%
- Avg arrival delay
- 9 min
- Arrived on time 83% of the time (53 flights, Jun 2025 to May 2026).
- Never cancelled in 54 scheduled flights.
- Short track record (53 flights), so its score leans on the airline's record at this hour.
Limited track record · 53 flights
Find Southwest 826 fares Opens this date on Aviasales#7 · Southwest 3964
10:25 AM → 11:35 AM1h 10m nonstop
Local times, typical schedule. Last flown 2026-05-27.
81%
chance on time
- On time (history)
- 81%
- Cancelled
- 0.0%
- Avg arrival delay
- 5 min
- Arrived on time 81% of the time (16 flights, Jun 2025 to May 2026).
- Lands inside MDW's trouble window: 50% of its 30 ground stops and delay programs started between 7 AM and 1 PM.
- Short track record (16 flights), so its score leans on the airline's record at this hour.
Limited track record · 16 flights
Find Southwest 3964 fares Opens this date on Aviasales#8 · Southwest 3166
8:45 PM → 9:50 PM1h 05m nonstop
Local times, typical schedule. Last flown 2026-05-31.
76%
chance on time
- On time (history)
- 83%
- Cancelled
- 0.0%
- Avg arrival delay
- 5 min
- Arrived on time 83% of the time (23 flights, Jun 2025 to May 2026).
- Short track record (23 flights), so its score leans on the airline's record at this hour.
Limited track record · 23 flights
Find Southwest 3166 fares Opens this date on Aviasales#9 · Southwest 3411
9:40 PM → 10:45 PM1h 05m nonstop
Local times, typical schedule. Last flown 2026-05-29.
75%
chance on time
- On time (history)
- 78%
- Cancelled
- 0.0%
- Avg arrival delay
- 19 min
- Arrived on time 78% of the time (23 flights, Jun 2025 to May 2026).
- Leaves in this route's least on-time window (After 9 PM: 66% on time; Before 9 AM: 92%).
- 70% of its delay minutes came from the plane arriving late from an earlier flight.
- Short track record (23 flights), so its score leans on the airline's record at this hour.
Limited track record · 23 flights
Find Southwest 3411 fares Opens this date on Aviasales#10 · Southwest 4549
9:50 PM → 11:00 PM1h 05m nonstop
Local times, typical schedule. Last flown 2026-04-06.
69%
chance on time
- On time (history)
- 59%
- Cancelled
- 3.0%
- Avg arrival delay
- 30 min
- Arrived on time 59% of the time (32 flights, Jun 2025 to May 2026).
- Cancelled 3.0% of the time (1 of 33).
- Leaves in this route's least on-time window (After 9 PM: 66% on time; Before 9 AM: 92%).
- Short track record (32 flights), so its score leans on the airline's record at this hour.
Limited track record · 32 flights
Find Southwest 4549 fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- Southwest Airlines80%
1,706 flights · 81% on time as flown · 1.1% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM92%
527 flights · avg delay 4 min
- 9 AM to noon85%
231 flights · avg delay 9 min
- Noon to 3 PM88%
243 flights · avg delay 7 min
- 3 to 6 PM68%
334 flights · avg delay 19 min
- 6 to 9 PM71%
293 flights · avg delay 18 min
- After 9 PM66%
78 flights · avg delay 27 min
Best day: Tuesday (86%). Worst: Sunday (78%).
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