Best Time to Fly SEA to PHL: On-Time Stats by Hour & Airline
Seattle/Tacoma International → Philadelphia International
Data through July 2026 · Last updated October 18, 2026
Over the last 12 months, 82.3% of Seattle (SEA) to Philadelphia (PHL) flights arrived on time (1,388 scheduled flights). That is 4.6 points above the national average of 77.6%.
Among 3 airlines, Delta Air Lines led with 84.2% on time and Alaska Airlines was last with 80.7%.
Over 24 months, Tuesday was the most reliable day (82% on time) and August the worst month (60%).
The cancellation rate was 1.5% (US average 1.8%).
SEA to PHL on-time performance by airline
Last 12 months. Airlines with fewer than 30 completed flights are marked “limited data”.
| Airline | On time | Avg delay when late | Cancelled | Flights |
|---|---|---|---|---|
| Delta Air Lines | 84.2% | 46 min | 1.2% | 83 |
| American Airlines | 83.7% | 86 min | 2.2% | 648 |
| Alaska Airlines | 80.7% | 44 min | 0.9% | 657 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly SEA to PHL
On-time arrival % by scheduled departure hour (local time), 2,400 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 6am–7am | 90.9% | 8.3% | 36 |
| 7am–8am | 81.8% | 0.0% | 33 |
| 8am–9am | 71.6% | 2.2% | 231 |
| 9am–10am | 76.3% | 0.6% | 638 |
| 12pm–1pm | 75.3% | 1.2% | 258 |
| 3pm–4pm | Limited data | 4 | |
| 9pm–10pm | 76.3% | 0.7% | 587 |
| 10pm–11pm | 83.4% | 2.2% | 406 |
| 11pm–12am | 76.5% | 2.4% | 207 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on SEA to PHL
On-time arrivals during holiday periods compared with all other days, last 24 months.
| Period | On time | vs other days | Cancelled | Flights |
|---|---|---|---|---|
| Thanksgiving week (Tue before to Mon after) | 77.1% | -2.5 pts | 0.0% | 35 |
| Christmas & New Year (Dec 20 - Jan 3) | 75.0% | -4.7 pts | 1.1% | 89 |
| Summer peak (Jun 15 - Aug 15) | 70.2% | -9.4 pts | 2.9% | 592 |
| All other days | 79.7% | — | 0.9% | 1,684 |
Monthly on-time trend
On-time arrival % each month, with the 12-month US average for reference.
What causes delays on this route
Share of reported delay minutes, last 12 months (BTS cause categories).