Schedule: a typical summer Sunday (the flights of Jul 26, 2026), re-dated. Real flights replace these once airlines file their FAA flight plans, usually about a day ahead.
SOUTHWEST · FLIGHT WN 3909
SCHEDULED · TYPICAL SCHEDULE
Sunday, October 4
WN 3909 · STL → DEN
departs 5:45 AM CT · arrives 7:00 AM MT
Forecast issued Fri 2:00 PM ET · 41h before departure
Watch this flight
Other days
Today 3%
Sat 10/3 2%
Sun 10/4
Mon 10/5 4%
Wed 10/7 3%
Odds over time
Arrive at DEN more than 15 minutes late?
2%
chance · ±1 pts
−1 pt · 24h
HOW SURE WE ARE
Moderate. The odds now blend history with early weather forecasts.
Arrive 15+ late
2%
Leave 15+ late
4%
Arrive 1h+ late
<1%
Cancelled
<1%
MOSTLY HISTORY
WEATHER FORECASTS
LIVE
IN THE AIR
0%
3%
6%
9%
12%
5.4d
2d
Now
1d
12h
6h
Departs
Lands
Arrive at DEN more than 15 minutes late?
Calm-weather odds: 2% · changed −1 pt in 24h
−1 pt
2%
Yes 2%
No 98%
Leave STL more than 15 minutes late?
Calm-weather odds: 3% · changed +1 pt in 24h
+1 pt
4%
Yes 4%
No 96%
Arrive at DEN more than an hour late?
Calm-weather odds: <1% · changed +0 pts in 24h
+0 pts
<1%
Yes <1%
No 99%
Cancelled?
Calm-weather odds: <1% · changed +0 pts in 24h
+0 pts
<1%
Yes <1%
No 100%
How late will it get to DEN?
On time or early
98%
15–30 min late
<1%
30 min–1 hour late
<1%
1–2 hours late
<1%
Over 2 hours late
<1%
Cancelled
<1%
Gate arrival compared with the scheduled arrival. The ranges add up to 100%.
What’s moving the odds
↑
DEN is busy at that time
↓
Early flights usually leave on time
↓
5am departures from STL are usually not late
Weather at each end
STL (origin)
Gusts 10 kt Ceiling none (clear) Visibility 10+ mi Precip none
DEN (destination)
Gusts 27 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.