Seattle (SEA) to Philadelphia (PHL): On-Time Performance
Data through July 2026
Seattle (SEA) to Philadelphia (PHL) effectively runs on two schedules. In April 2026, 94% of arrivals were on time; in August 2024 that fell to 46% — a 48-point seasonal swing. Across the full period the route averages 76% on-time against a national 78%.
- On-time
- 76%
- arrived <15 min late
- Avg delay
- 14 min
- completed flights
- Cancelled
- 1.3%
- Flights/day
- 3.8
- last 12 months
- Duration
- 5h 10m
- scheduled
- Distance
- 2,379 mi
Best airline from SEA to PHL
3 airlines flew this route regularly between 2024-07 and 2026-07.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| Delta Air Linesmost reliable | 84% | 8 min | 1.2% | 83 |
| American Airlines | 77% | 17 min | 2.2% | 1,083 |
| Alaska Airlines | 74% | 12 min | 0.7% | 1,357 |
Monthly on-time trend
Best time to fly from SEA to PHL
Aim for departures around 6 a.m. (91% on-time); avoid 8 a.m. departures (70%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 76% | 15 min |
| Tuesday | 79% | 10 min |
| Wednesdaybest | 79% | 9 min |
| Thursday | 72% | 15 min |
| Friday | 74% | 19 min |
| Saturday | 78% | 10 min |
| Sunday | 73% | 20 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft38%
- Airline operations35%
- National airspace system20%
- Weather6%
Frequently asked questions
- How often are flights from SEA to PHL delayed?
- 24% of SEA–PHL flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-07 and 2026-07. The average arrival delay across completed flights was 14 minutes.
- Which airline is most reliable from SEA to PHL?
- Delta Air Lines has the best on-time record on this route at 84%, based on 83 flights. 3 airlines flew SEA–PHL frequently enough to compare in this period.
- What is the best time of day to fly from SEA to PHL?
- Departures around 6 a.m. have the best record (91% on-time), while departures around 8 a.m. have the worst (70%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from SEA to PHL?
- The scheduled SEA–PHL flight time averages 5h 10m over 2,379 miles. Actual arrival times vary — flights on this route land 15+ minutes late 24% of the time.
- How often are SEA to PHL flights cancelled?
- 1.3% of scheduled flights on this route were cancelled between 2024-07 and 2026-07, at or below the national rate of 1.6%.
- What is the worst month to fly from SEA to PHL?
- August 2024 was the roughest month in this dataset, with only 46% of arrivals on time. The best was April 2026 at 94%. If your dates are flexible, that 48-point gap is worth planning around.
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Based on 2,523 flights, 2024-07–2026-07. Source: US DOT Bureau of Transportation Statistics. Updated 2026-09-28.