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Route on-time record

STL to MDW: most on-time flights and the best time to fly

St Louis (St. Louis Lambert International Airport) to Chicago (Chicago Midway International Airport). 1,706 nonstop flights in Jun 2025 to May 2026, 81% arrived within 15 minutes and 1.1% were cancelled. The most reliable flight number was Southwest 4489 at 5:40 AM.

Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.

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

Check STL to MDW fares

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. #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. #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. #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. #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. #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. #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. #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. #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. #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. #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%).

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.

J
85
F
92
M
82
A
85
M
80
J
80
J
71
A
79
S
86
O
86
N
90
D
83

What delays this route

  • Late-arriving aircraft53%
  • Airline (crew, maintenance, boarding)25%
  • Air traffic control and airport volume19%
  • Severe weather3%

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

STL to MDW questions

What time of day is best to fly STL to MDW?
Before 9 AM: 92% of flights arrived on time, against 66% for departures after 9 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 STL to MDW?
Southwest, with a season-adjusted 80% chance of operating and arriving on time over 1,706 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 STL to MDW?
July (71% on time); the best was February (92%), 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 STL

Live status: FAA delays and ground stops