Schedule: a typical Saturday (the flights of Jul 25, 2026, re-dated). Real flights replace these once the FAA publishes them, usually about a day ahead.
DELTA · FLIGHT DL 821SCHEDULED · TYPICAL SCHEDULE
DL 821 · ATL → BOS
departs 6:15 PM ET · arrives 9:00 PM ET
Forecast issued Thu 3:00 PM ET · 51h before departure
Odds over time
Arrive at BOS more than 15 minutes late?
20%chance · ±3 pts– · 24h
HOW SURE WE AREModerate. 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
9%
30 min–1 hour late
5%
1–2 hours late
4%
Over 2 hours late
2%
Cancelled
<1%
Gate arrival compared with the scheduled arrival. The ranges add up to 100%.