UA521
UA521 (United Airlines) is a multi-stop service on 21 routes, busiest Boston to Newark. Of 689 departures recorded from October 2024 to July 2026, 68.8% left on time, according to the US BTS.
- On-time departures68.8%of 689 flights
- Average delay24.7 min
- July 202631▲ 0.0%vs July 2025
- Cancelled2.3%
- Legs flown under this number21
Recorded departures by month
All legs under this number combined; see the leg table.
The most recent periods19 periods
| Period | Departures 2025 | Departures 2026 | Change vs last year |
|---|---|---|---|
| January | 25 | 31 | ▲ 24.0% |
| February | 24 | 40 | ▲ 66.7% |
| March | 31 | 55 | ▲ 77.4% |
| April | 30 | 55 | ▲ 83.3% |
| May | 31 | 44 | ▲ 41.9% |
| June | 30 | 21 | ▼ 30.0% |
| July | 31 | 31 | 0.0% |
| August | 29 | – | – |
| September | 25 | – | – |
| October | 31 | – | in progress |
| November | 24 | – | – |
| December | 31 | – | – |
| Year to date (Jan–Jul) | 202 | 277 | ▲ 37.1% |
according to the US BTS · October 2024 → July 2026
On-time departures by month
On time = departure within 15 minutes of schedule. Non-cancelled flights with a recorded delay only.
The most recent periods19 periods
| Period | On time 2025 | On time 2026 | Change vs last year |
|---|---|---|---|
| January | 64.0% | 85.7% | ▲ 33.9% |
| February | 75.0% | 89.7% | ▲ 19.7% |
| March | 67.7% | 72.7% | ▲ 7.4% |
| April | 58.6% | 70.9% | ▲ 21.0% |
| May | 96.7% | 68.2% | ▼ 29.5% |
| June | 93.3% | 52.4% | ▼ 43.9% |
| July | 71.4% | 58.1% | ▼ 18.7% |
| August | 72.4% | – | – |
| September | 45.8% | – | – |
| October | 31.0% | – | in progress |
| November | 61.9% | – | – |
| December | 63.3% | – | – |
| Year-to-date average (Jan–Jul) | 75.3% | 71.1% | ▼ 5.5% |
according to the US BTS · October 2024 → July 2026
Average departure delay by month
according to the US BTS · October 2024 → July 2026
Cancelled departures by month
The most recent periods19 periods
| Period | Cancelled 2025 | Cancelled 2026 | Change vs last year |
|---|---|---|---|
| January | 0 | 3 | – |
| February | 0 | 1 | – |
| March | 0 | 0 | – |
| April | 1 | 0 | ▼ 100.0% |
| May | 1 | 0 | ▼ 100.0% |
| June | 0 | 0 | – |
| July | 3 | 0 | ▼ 100.0% |
| August | 0 | – | – |
| September | 1 | – | – |
| October | 2 | – | in progress |
| November | 3 | – | – |
| December | 1 | – | – |
| Year to date (Jan–Jul) | 5 | 4 | ▼ 20.0% |
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 97.7% 673
- Cancelled 2.3% 16
Share of all recorded flights in the period, all legs. · Oct 13, 2024 → Jul 31, 2026
On time, leg by leg
Departures within 15 minutes of schedule; small figure = departures recorded.
Legs flown under this number
5| Routes | Distance (km) | Avg delay | On time | Departures |
|---|---|---|---|---|
| BOS EWR Boston Logan International Airport – Newark Liberty International Airport | 322 | 39.5 min | 60.1% | 282 |
| IAH BOS George Bush Intercontinental Airport – Boston Logan International Airport | 2,567 | 23.2 min | 60.5% | 124 |
| ATL IAH Hartsfield Jackson Atlanta International Airport – George Bush Intercontinental Airport | 1,108 | 15.2 min | 78.4% | 88 |
| BNA SFO Nashville International Airport – San Francisco International Airport | 3,161 | 16.9 min | 69.7% | 36 |
| BOS IAD Boston Logan International Airport – Washington Dulles International Airport | 663 | -4.0 min | 100.0% | 35 |
Monthly figures
| Period | Departures | With departure delay recorded | On time | Cancelled |
|---|---|---|---|---|
| October 2024 | 17 | 17 | 64.7% | 0 |
| November 2024 | 24 | 24 | 62.5% | 0 |
| December 2024 | 29 | 29 | 62.1% | 0 |
| January 2025 | 25 | 25 | 64.0% | 0 |
| February 2025 | 24 | 24 | 75.0% | 0 |
| March 2025 | 31 | 31 | 67.7% | 0 |
| April 2025 | 30 | 29 | 58.6% | 1 |
| May 2025 | 31 | 30 | 96.7% | 1 |
| June 2025 | 30 | 30 | 93.3% | 0 |
| July 2025 | 31 | 28 | 71.4% | 3 |
| August 2025 | 29 | 29 | 72.4% | 0 |
| September 2025 | 25 | 24 | 45.8% | 1 |
| October 2025 | 31 | 29 | 31.0% | 2 |
| November 2025 | 24 | 21 | 61.9% | 3 |
| December 2025 | 31 | 30 | 63.3% | 1 |
| January 2026 | 31 | 28 | 85.7% | 3 |
| February 2026 | 40 | 39 | 89.7% | 1 |
| March 2026 | 55 | 55 | 72.7% | 0 |
| April 2026 | 55 | 55 | 70.9% | 0 |
| May 2026 | 44 | 44 | 68.2% | 0 |
| June 2026 | 21 | 21 | 52.4% | 0 |
| July 2026 | 31 | 31 | 58.1% | 0 |