Friday, October 9 · typical odds for a Friday (too early for a weather forecast) · issued Sun 4:00 PM ET · 11 nonstops

Fri, Oct 9: WN 4939 at 05:40 is the safest bet, 5% chance of being 15+ min late; the others run 6–37%.

Safest bet that day WN 4939 STL 05:40 → LGA 09:00 · 5% chance 15+ min late · usually 96% on time Riskiest WN 4684 STL 19:55 → LGA 23:25 · 37% chance 15+ min late · usually 41% on time

Every nonstop on Fri, Oct 9

12-month record →

Ranked by the chance of arriving 15+ minutes late (typical odds: the weather this date has had in past years), with each flight’s on-time record over Aug 2025 – Jul 2026 beside it. Times are local. Pick a flight for its forecast. Click a column to sort. Dimmed: airlines we don’t forecast yet, shown with their 12-month record if they usually fly that weekday.


WN 4939 Southwest Flight history →	STL 05:40	LGA 09:00	5%	1%	0.8%	96%
AA 4669 American flown by Republic Flight history →	STL 06:00	LGA 09:35	6%	2%	0.8%	90%
AA 4508 American flown by Republic Flight history →	STL 09:22	LGA 12:56	11%	3%	0.8%	84%
WN 1373 Southwest Flight history →	STL 11:00	LGA 14:25	19%	4%	0.9%	82%
AA 4509 American flown by Republic Flight history →	STL 15:20	LGA 18:55	21%	6%	1.0%	71%
WN 4962 Southwest Flight history →	STL 15:25	LGA 18:55	34%	8%	0.8%	63%
WN 4684 Southwest Flight history →	STL 19:55	LGA 23:25	37%	9%	0.8%	41%
DL 4981 Delta flown by Endeavor no forecast: 12-month record	STL 06:05	LGA 09:38	10%	6%	2.1%	90%
DL 4935 Delta flown by Endeavor no forecast: 12-month record	STL 17:22	LGA 21:00	21%	13%	18.8%	79%
DL 4839 Delta flown by Endeavor no forecast: 12-month record	STL 09:22	LGA 12:56	23%	5%	10.4%	77%
DL 4922 Delta flown by Endeavor no forecast: 12-month record	STL 12:35	LGA 16:09	26%	14%	5.4%	74%

How these are worked out. Each flight’s odds are our forecast for that day (typical odds until the weather forecast covers it); flights of airlines we don’t forecast yet use their 12-month record and are marked. Makes the connection: the first flight’s 12-month lateness curve, scaled so its chance of arriving 15+ min late matches the day’s forecast, at the layover minus the 45-minute minimum (90 on separate tickets). Arrives on time: first flight not cancelled × connection made × second flight not cancelled × second flight within 15 minutes, each from the day’s forecast.

About this data: forecast odds from our model for Fri, Oct 9 (newest published update); 12-month records from US DOT on-time data, Aug 2025 – Jul 2026, all US airlines; regional flights count under the airline that sells them. JSON