WN4217
WN4217 (Southwest Airlines) is a multi-stop service on 25 routes, busiest Boston to St Louis. Of 423 departures recorded from October 2024 to July 2026, 69.7% left on time, according to the US BTS.
- On-time departures69.7%of 423 flights
- Average delay17.0 min
- July 202621▲ 16.7%vs July 2025
- Cancelled1.0%
- Legs flown under this number25
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 | 11 | 5 | ▼ 54.5% |
| February | 7 | 10 | ▲ 42.9% |
| March | 2 | 40 | ▲ 1,900.0% |
| April | 22 | 22 | 0.0% |
| May | 17 | 18 | ▲ 5.9% |
| June | 16 | 21 | ▲ 31.3% |
| July | 18 | 21 | ▲ 16.7% |
| August | 36 | – | – |
| September | 39 | – | – |
| October | 1 | – | in progress |
| November | 22 | – | – |
| December | 16 | – | – |
| Year to date (Jan–Jul) | 93 | 137 | ▲ 47.3% |
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 | 66.7% | 80.0% | ▲ 20.0% |
| February | 71.4% | 70.0% | ▼ 2.0% |
| March | 50.0% | 55.0% | ▲ 10.0% |
| April | 81.8% | 45.5% | ▼ 44.5% |
| May | 94.1% | 17.7% | ▼ 81.2% |
| June | 87.5% | 52.4% | ▼ 40.1% |
| July | 100.0% | 66.7% | ▼ 33.3% |
| August | 83.3% | – | – |
| September | 84.6% | – | – |
| October | 0.0% | – | in progress |
| November | 81.0% | – | – |
| December | 50.0% | – | – |
| Year-to-date average (Jan–Jul) | 78.8% | 55.3% | ▼ 29.8% |
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 | 2 | 0 | ▼ 100.0% |
| February | 0 | 0 | – |
| March | 0 | 0 | – |
| April | 0 | 0 | – |
| May | 0 | 1 | – |
| June | 0 | 0 | – |
| July | 0 | 0 | – |
| August | 0 | – | – |
| September | 0 | – | – |
| October | 0 | – | in progress |
| November | 1 | – | – |
| December | 0 | – | – |
| Year to date (Jan–Jul) | 2 | 1 | ▼ 50.0% |
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 99.1% 419
- Cancelled 0.9% 4
Share of all recorded flights in the period, all legs. · Oct 14, 2024 → Jul 31, 2026
On time, leg by leg
Departures within 15 minutes of schedule; small figure = departures recorded.
Legs flown under this number
6| Routes | Distance (km) | Avg delay | On time | Departures |
|---|---|---|---|---|
| BOS STL Boston Logan International Airport – St. Louis Lambert International Airport | 1,680 | 15.7 min | 71.4% | 72 |
| SAN SJC San Diego International Airport – Mineta San Jose International Airport | 671 | 6.9 min | 86.0% | 50 |
| BWI MDW Baltimore/Washington International Thurgood Marshall Airport – Chicago Midway International Airport | 981 | 15.2 min | 61.8% | 34 |
| BWI BOS Baltimore/Washington International Thurgood Marshall Airport – Boston Logan International Airport | 594 | 5.3 min | 94.1% | 34 |
| PHX HOU Phoenix Sky Harbor International Airport – William P. Hobby Airport | 1,638 | 35.0 min | 48.5% | 33 |
| SFO SAN San Francisco International Airport – San Diego International Airport | 719 | 62.6 min | 22.6% | 32 |
Monthly figures
| Period | Departures | With departure delay recorded | On time | Cancelled |
|---|---|---|---|---|
| October 2024 | 21 | 21 | 57.1% | 0 |
| November 2024 | 28 | 28 | 75.0% | 0 |
| December 2024 | 30 | 30 | 73.3% | 0 |
| January 2025 | 11 | 9 | 66.7% | 2 |
| February 2025 | 7 | 7 | 71.4% | 0 |
| March 2025 | 2 | 2 | 50.0% | 0 |
| April 2025 | 22 | 22 | 81.8% | 0 |
| May 2025 | 17 | 17 | 94.1% | 0 |
| June 2025 | 16 | 16 | 87.5% | 0 |
| July 2025 | 18 | 18 | 100.0% | 0 |
| August 2025 | 36 | 36 | 83.3% | 0 |
| September 2025 | 39 | 39 | 84.6% | 0 |
| October 2025 | 1 | 1 | 0.0% | 0 |
| November 2025 | 22 | 21 | 81.0% | 1 |
| December 2025 | 16 | 16 | 50.0% | 0 |
| January 2026 | 5 | 5 | 80.0% | 0 |
| February 2026 | 10 | 10 | 70.0% | 0 |
| March 2026 | 40 | 40 | 55.0% | 0 |
| April 2026 | 22 | 22 | 45.5% | 0 |
| May 2026 | 18 | 17 | 17.7% | 1 |
| June 2026 | 21 | 21 | 52.4% | 0 |
| July 2026 | 21 | 21 | 66.7% | 0 |