Schedule: a typical summer Friday (the flights of Jul 31, 2026), re-dated. Real flights replace these once airlines file their FAA flight plans, usually about a day ahead.
SOUTHWEST · FLIGHT WN 4121
SCHEDULED · TYPICAL SCHEDULE
Friday, October 2 Yesterday
WN 4121 · MDW → SMF
departs 9:55 PM CT · arrives 12:25 AM PT
Forecast issued Fri 10:00 PM ET · 1h before departure
Watch this flight
Other days
Fri 10/2
Today 30%
Sun 10/4 33%
Mon 10/5 28%
Fri 10/9 36%
Odds over time
Arrive at SMF more than 15 minutes late?
37%
chance · ±0 pts
+5 pts · 24h
HOW SURE WE ARE
Very high. The odds now come almost entirely from live conditions.
Arrive 15+ late
37%
Leave 15+ late
47%
Arrive 1h+ late
10%
Cancelled
<1%
WEATHER FORECASTS
LIVE
IN THE AIR
0%
20%
40%
60%
80%
4.0d
2d
1d
12h
6h
Now
Departs
Lands
Arrive at SMF more than 15 minutes late?
Calm-weather odds: 41% · changed +5 pts in 24h
+5 pts
37%
Yes 37%
No 63%
Leave MDW more than 15 minutes late?
Calm-weather odds: 47% · changed +0 pts in 24h
+0 pts
47%
Yes 47%
No 53%
Arrive at SMF more than an hour late?
Calm-weather odds: 10% · changed +1 pt in 24h
+1 pt
10%
Yes 10%
No 90%
Cancelled?
Calm-weather odds: <1% · changed +0 pts in 24h
+0 pts
<1%
Yes <1%
No 99%
How late will it get to SMF?
On time or early
62%
15–30 min late
10%
30 min–1 hour late
17%
1–2 hours late
8%
Over 2 hours late
2%
Cancelled
<1%
Gate arrival compared with the scheduled arrival. The ranges add up to 100%.
What’s moving the odds
↑
9pm departures from MDW are often late
↑
Later flights pick up delays from earlier in the day
↑
This flight has been late 45% of the time recently
↓
Mostly benign weather forecast at SMF
↓
Cloud base down to 900 ft forecast at MDW that day
Weather at each end
MDW (origin)
Gusts 15 kt Ceiling 900 ft Visibility 7 mi Precip 0.12 in
SMF (destination)
Gusts 8 kt Ceiling none (clear) Visibility 10+ mi Precip none
How this resolves
Yes if the gate arrival is more than 15 minutes after the scheduled arrival. Cancelled or diverted flights resolve N/A.
Every question here is display only — there is no betting or money involved. Gate times come from the airline; a cancellation resolves only the “Cancelled?” question, and a diversion voids the delay questions.