DL399
DL399 (Delta Air Lines) is a multi-stop service on 3 routes, busiest Boston to Atlanta. Of 509 departures recorded from October 2024 to July 2026, 68.0% left on time, according to the US BTS.
- On-time departures68.0%of 509 flights
- Average delay21.5 min
- July 202627▼ 12.9%vs July 2025
- Cancelled0.6%
- Legs flown under this number3
Recorded departures by month
All legs under this number combined; see the leg table.
Months without data are left blank.
The most recent periods16 periods
| Period | Departures 2025 | Departures 2026 | Change vs last year |
|---|---|---|---|
| January | 26 | – | – |
| February | 28 | – | – |
| March | 31 | – | – |
| April | 30 | 24 | ▼ 20.0% |
| May | 31 | 31 | 0.0% |
| June | 30 | 27 | ▼ 10.0% |
| July | 31 | 27 | ▼ 12.9% |
| August | 31 | – | – |
| September | 30 | – | – |
| October | 31 | – | in progress |
| November | 30 | – | – |
| December | 19 | – | – |
according to the US BTS · October 2024 → July 2026
On-time departures by month
Months without data are left blank.
On time = departure within 15 minutes of schedule. Non-cancelled flights with a recorded delay only.
The most recent periods16 periods
| Period | On time 2025 | On time 2026 | Change vs last year |
|---|---|---|---|
| January | 69.2% | – | – |
| February | 75.0% | – | – |
| March | 71.0% | – | – |
| April | 75.9% | 66.7% | ▼ 12.1% |
| May | 48.4% | 83.9% | ▲ 73.3% |
| June | 60.0% | 70.4% | ▲ 17.3% |
| July | 60.0% | 55.6% | ▼ 7.4% |
| August | 67.7% | – | – |
| September | 36.7% | – | – |
| October | 51.6% | – | in progress |
| November | 80.0% | – | – |
| December | 55.6% | – | – |
according to the US BTS · October 2024 → July 2026
Average departure delay by month
Months without data are left blank.
according to the US BTS · October 2024 → July 2026
Cancelled departures by month
Months without data are left blank.
The most recent periods16 periods
| Period | Cancelled 2025 | Cancelled 2026 | Change vs last year |
|---|---|---|---|
| January | 0 | – | – |
| February | 0 | – | – |
| March | 0 | – | – |
| April | 1 | 0 | ▼ 100.0% |
| May | 0 | 0 | – |
| June | 0 | 0 | – |
| July | 1 | 0 | ▼ 100.0% |
| August | 0 | – | – |
| September | 0 | – | – |
| October | 0 | – | in progress |
| November | 0 | – | – |
| December | 1 | – | – |
according to the US BTS · October 2024 → July 2026
This is a historical record of departures already flown, not a forecast for your flight.
Several legs: the headline figure averages all of them. See the leg table.
Cancellation share
- Not cancelled 99.4% 506
- Cancelled 0.6% 3
Share of all recorded flights in the period, all legs. · Oct 12, 2024 → Jul 31, 2026
On time, leg by leg
Departures within 15 minutes of schedule; small figure = departures recorded.
Legs flown under this number
2| Routes | Distance (km) | Avg delay | On time | Departures |
|---|---|---|---|---|
| BOS ATL Boston Logan International Airport – Hartsfield Jackson Atlanta International Airport | 1,521 | 25.0 min | 63.8% | 451 |
| DEN ATL Denver International Airport – Hartsfield Jackson Atlanta International Airport | 1,927 | -6.7 min | 100.0% | 52 |
Monthly figures
| Period | Departures | With departure delay recorded | On time | Cancelled |
|---|---|---|---|---|
| October 2024 | 15 | 15 | 100.0% | 0 |
| November 2024 | 19 | 19 | 100.0% | 0 |
| December 2024 | 18 | 18 | 100.0% | 0 |
| January 2025 | 26 | 26 | 69.2% | 0 |
| February 2025 | 28 | 28 | 75.0% | 0 |
| March 2025 | 31 | 31 | 71.0% | 0 |
| April 2025 | 30 | 29 | 75.9% | 1 |
| May 2025 | 31 | 31 | 48.4% | 0 |
| June 2025 | 30 | 30 | 60.0% | 0 |
| July 2025 | 31 | 30 | 60.0% | 1 |
| August 2025 | 31 | 31 | 67.7% | 0 |
| September 2025 | 30 | 30 | 36.7% | 0 |
| October 2025 | 31 | 31 | 51.6% | 0 |
| November 2025 | 30 | 30 | 80.0% | 0 |
| December 2025 | 19 | 18 | 55.6% | 1 |
| April 2026 | 24 | 24 | 66.7% | 0 |
| May 2026 | 31 | 31 | 83.9% | 0 |
| June 2026 | 27 | 27 | 70.4% | 0 |
| July 2026 | 27 | 27 | 55.6% | 0 |