Schedule: a typical Wednesday (the flights of Jul 29, 2026, re-dated). Real flights replace these once the FAA publishes them, usually about a day ahead.
SOUTHWEST · FLIGHT WN 3891
SCHEDULED · TYPICAL SCHEDULE
Wednesday, September 30 Today
WN 3891 · STL → BOS
departs 10:15 AM CT · arrives 1:50 PM ET
Forecast issued Wed 12:00 PM ET · 1h after departure
Watch this flight
Other days
Today
Thu 10/1 15%
Fri 10/2 24%
Sun 10/4 14%
Mon 10/5 20%
Tue 10/6 14%
Odds over time
Arrive at BOS more than 15 minutes late?
19%
chance · ±1 pts
+3 pts · 24h
HOW SURE WE ARE
Very high. The odds now come almost entirely from live conditions.
Arrive 15+ late
19%
Leave 15+ late
16%
Arrive 1h+ late
3%
Cancelled
<1%
WEATHER FORECASTS
LIVE
IN THE AIR
0%
10%
20%
30%
40%
2.9d
2d
1d
12h
6h
Departs
Lands
Arrive at BOS more than 15 minutes late?
Calm-weather odds: 18% · changed +3 pts in 24h
+3 pts
19%
Yes 19%
No 81%
Leave STL more than 15 minutes late?
Calm-weather odds: 15% · changed +4 pts in 24h
+4 pts
16%
Yes 16%
No 84%
Arrive at BOS more than an hour late?
Calm-weather odds: 3% · changed +0 pts in 24h
+0 pts
3%
Yes 3%
No 97%
Cancelled?
Calm-weather odds: <1% · changed +0 pts in 24h
+0 pts
<1%
Yes <1%
No 99%
How late will it get to BOS?
On time or early
81%
15–30 min late
9%
30 min–1 hour late
7%
1–2 hours late
3%
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
↑
This flight has been late 21% of the time recently
↑
BOS is prone to delays
↑
Cloud base down to 700 ft, visibility down to 2 mi forecast at BOS that day
↓
Wednesdays in September are usually quieter than average
↓
Mostly benign weather forecast at STL
Weather at each end
STL (origin)
Gusts 14 kt Ceiling 9,000 ft Visibility 10+ mi Precip none
BOS (destination)
Gusts 8 kt Ceiling 700 ft Visibility 2 mi Precip 0.02 in
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.