Schedule: a typical Thursday (the flights of Jul 30, 2026, re-dated). Real flights replace these once the FAA publishes them, usually about a day ahead.
SOUTHWEST · FLIGHT WN 3966
SCHEDULED · TYPICAL SCHEDULE
Thursday, October 1 Tomorrow
WN 3966 · STL → PHL
departs 8:40 PM CT · arrives 11:55 PM ET
Forecast issued Tue 11:00 PM ET · 47h before departure
Watch this flight
Other days
Today 20%
Thu 10/1
Fri 10/2 31%
Sun 10/4 29%
Mon 10/5 21%
Tue 10/6 19%
Odds over time
Arrive at PHL more than 15 minutes late?
37%
chance · ±4 pts
+0 pts · 24h
HOW SURE WE ARE
Moderate. The odds now blend history with early weather forecasts.
Arrive 15+ late
37%
Leave 15+ late
51%
Arrive 1h+ late
9%
Cancelled
<1%
WEATHER FORECASTS
LIVE
IN THE AIR
0%
15%
30%
45%
60%
2.8d
Now
1d
12h
6h
Departs
Lands
Arrive at PHL more than 15 minutes late?
Calm-weather odds: 22% · changed +0 pts in 24h
+0 pts
37%
Yes 37%
No 63%
Leave STL more than 15 minutes late?
Calm-weather odds: 37% · changed +0 pts in 24h
+0 pts
51%
Yes 51%
No 49%
Arrive at PHL more than an hour late?
Calm-weather odds: 5% · changed −1 pt in 24h
−1 pt
9%
Yes 9%
No 91%
Cancelled?
Calm-weather odds: <1% · changed +0 pts in 24h
+0 pts
<1%
Yes <1%
No 99%
How late will it get to PHL?
On time or early
63%
15–30 min late
9%
30 min–1 hour late
18%
1–2 hours late
6%
Over 2 hours late
3%
Cancelled
<1%
Gate arrival compared with the scheduled arrival. The ranges add up to 100%.
What’s moving the odds
↑
Mostly benign weather forecast at STL
↑
WN's recent on-time record
↑
Later flights pick up delays from earlier in the day
↓
Mostly benign weather forecast at PHL
↓
STL usually runs smoothly
Weather at each end
STL (origin)
Gusts 16 kt Ceiling 4,000 ft Visibility 10+ mi Precip 0.18 in
PHL (destination)
Gusts 10 kt Ceiling 9,000 ft 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.