About 1 in 2 DL 5666 flights from Boston arrived 15+ minutes late, diverted or cancelled over the past year (47%); 6.6% were cancelled. The typical flight landed 6 minutes late.
DL 5666: BOS → DCA
Scheduled to leave Boston at 8:15 p.m. local time, operated by Republic Airways as YX 5666. Over the past year it arrived on time 53% of the time (229 flights), better than other DL flights on the route at that hour (49%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 37 | 62% |
| Tuesday | 36 | 64% |
| Wednesday | 34 | 53% |
| Thursday | 34 | 41% |
| Friday | 36 | 50% |
| Saturday | 15 | — |
| Sunday | 37 | 38% |
Why it was late
All flights BOS → DCA · Connecting off DL 5666? Check the risk
Questions
How often is DL 5666 from BOS to DCA late?
Delta Air Lines 5666 from Boston, MA to Washington, DC arrived 15 or more minutes late, was diverted or was cancelled on 47% of 229 scheduled flights between September 2025 and August 2026. 6.6% 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.