Schedule: a typical Sunday (the flights of Jul 26, 2026, re-dated). Real flights replace these once the FAA publishes them, usually about a day ahead.

DELTA · FLIGHT DL 821 SCHEDULED · TYPICAL SCHEDULE

Sunday, October 4

DL 821 · ATL → BOS

departs 9:05 AM ET · arrives 11:40 AM ET

Forecast issued Thu 5:00 PM ET · 64h before departure

Arrive at BOS more than 15 minutes late?

20% chance · ±1 pts +8 pts · 24h

HOW SURE WE ARE Moderate. The odds now blend history with early weather forecasts.

How late will it get to BOS?

On time or early
79%
15–30 min late
7%
30 min–1 hour late
10%
1–2 hours late
2%
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

↑ Cloud base down to 300 ft, visibility down to 2 mi, 0.7 in of rain forecast at ATL that day

↑ This flight has been late 30% of the time recently

↑ Other factors

↓ BOS usually runs smoothly

↓ Mostly benign weather forecast at BOS

Weather at each end

ATL (origin) Gusts10 kt Ceiling300 ft Visibility2 mi Precip0.67 in

BOS (destination) Gusts14 kt Ceilingnone (clear) Visibility10+ mi Precipnone

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.

DL 821 · ATL → BOS

Odds over time

How late will it get to BOS?