About 1 in 6 DL 1399 flights from Boston arrived 15+ minutes late, diverted or cancelled over the past year (18%); 2.0% were cancelled. The typical flight landed 7 minutes early.
DL 1399: BOS → MIA
Scheduled to leave Boston at 7:05 a.m. local time. Over the past year it arrived on time 82% of the time (345 flights), in line with other DL flights on the route at that hour (82%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 51 | 78% |
| Tuesday | 50 | 84% |
| Wednesday | 50 | 88% |
| Thursday | 50 | 76% |
| Friday | 50 | 86% |
| Saturday | 45 | 84% |
| Sunday | 49 | 80% |
Why it was late
All flights BOS → MIA · Connecting off DL 1399? Check the risk
DL 1399: MIA → BOS
Scheduled to leave Miami at 11:50 a.m. local time. Over the past year it arrived on time 70% of the time (227 flights), in line with other DL flights on the route at that hour (72%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 33 | 61% |
| Tuesday | 32 | 78% |
| Wednesday | 32 | 84% |
| Thursday | 33 | 55% |
| Friday | 33 | 64% |
| Saturday | 32 | 75% |
| Sunday | 32 | 72% |
Why it was late
All flights MIA → BOS · Connecting off DL 1399? Check the risk
Questions
How often is DL 1399 from BOS to MIA late?
Delta Air Lines 1399 from Boston, MA to Miami, FL arrived 15 or more minutes late, was diverted or was cancelled on 18% of 345 scheduled flights between September 2025 and August 2026. 2.0% were cancelled.
How often is DL 1399 from MIA to BOS late?
Delta Air Lines 1399 from Miami, FL to Boston, MA arrived 15 or more minutes late, was diverted or was cancelled on 30% of 227 scheduled flights between September 2025 and August 2026. 0.4% were cancelled.
Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check Delta Air Lines for today's flight. Method.