Carrier route record
ASSEA→PHL
Alaska Airlines · Seattle to Philadelphia
- Flights
- 657
- Period
- September 2025 to August 2026
- Share of route
- 46%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on SEA to PHL lands a B, 3 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 45 minutes on average. That rests on 657 flights, with a median arrival 6 minutes early.
The US average over the same twelve months is 77.3%, so there is little to separate Alaska on SEA to PHL from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.7%
Arrivals under 15 minutes late, of 646 completed flights
Avg delay
46 min
Across delayed arrivals only, not all flights
Cancelled
1.07%
National rate is 1.89%
Whole route
82.7%
Every carrier on SEA to PHL, 1,431 flights
These figures cover 657 flights between September 2025 and August 2026. The median arrival is 6 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
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Carrier by carrier
Alaska against every carrier on SEA to PHL
Alaska flew 657 of the 1,431 flights on SEA to PHL, about 46% of it. Its 80.7% on time is 2 points worse than the route as a whole, which runs 82.7%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from American at 84.6% to Alaska at 80.7%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 660 | 84.6% | 104 min | 2.12% | B |
| Delta Air Linesthin sample | 114 | 83.2% | 54 min | 0.88% | B+ |
| Alaska Airlines (this page) | 657 | 80.7% | 46 min | 1.07% | B |
Flight by flight
Alaska flight numbers on SEA to PHL
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Departure window
When Alaska runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am364 flights74.9%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm—
- 8pm–5am293 flights87.7%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
The overnight block holds up unusually well at 87.7% on time across 293 flights. Red-eyes fly into empty airspace and empty gates, and they are the first rotation of the aircraft's day rather than the last. The 8am–11am window is the busiest, with 364 flights scheduled in it.
Across the year
Alaska on SEA to PHL through the year
January is the weak month at 65.7% on time, against 96.7% in April. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. May was the busiest month here, with 62 flights.
Across the week, Tuesday is the strongest day at 84.8% on time and Thursday the weakest at 72.5%, a spread of 12 points.
Arrival by arrival
How late Alaska on SEA to PHL runs when it is late
Alaska on SEA to PHL often beats the schedule: 190 of 646 completed flights, 29%, arrived 15 minutes or more early. The 125 late arrivals split 54 under half an hour, 44 between 30 and 60 minutes, and 27 an hour or more.
- 15+ min early190 flights29.4%
- Within 15 min331 flights51.2%
- 15–29 min late54 flights8.4%
- 30–59 min late44 flights6.8%
- 1–2 hours late20 flights3.1%
- 2+ hours late7 flights1.1%
Scale runs 0% to 100%.
Share of 646 completed flights by arrival against schedule.
A late pushback is often recovered here: of 151 departures that left 15 minutes late or more, 57 still arrived on time. 31 flights left on time and still arrived late.
The worst days
Worst days for Alaska on SEA to PHL
The latest arrival of the period was on 13 March 2026, 5 hours 26 minutes behind schedule; most of its delay minutes were filed as extreme weather. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 13 March 2026 | 5 hours 26 minutes | Extreme weather |
| 2 August 2026 | 3 hours 1 minute | Carrier |
| 1 October 2025 | 2 hours 50 minutes | Carrier |
| 11 July 2026 | 2 hours 27 minutes | Carrier |
| 27 August 2026 | 2 hours 21 minutes | National Airspace System |
Delay causes
Why Alaska runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 5,733 reported delay minutes.
- 38%Carrier
- 27%Late-arriving aircraft
- 25%National Airspace System
- 11%Extreme weather
The largest share of delay minutes, 38%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,190 of the 5,733 delay minutes reported here. The split is drawn from 5,733 reported delay minutes.
Cancellations sit at 1.07% against a national 1.89%, which is ordinary. Diversions add another 0.61%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.2% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
At 2,379 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 68.0% on time across 657 flights, 13 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 13 points of difference.
One caution: this is a thin sample. 657 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Alaska on SEA to PHL
Put together: treat all of this as provisional. 657 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 80.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 646 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to PHL, every carrier
- Alaska on PHL to SEA, the return leg
- American Airlines on SEA to PHL84.6%
- Delta Air Lines on SEA to PHL83.2%
- Alaska Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Philadelphia International (PHL) delay statistics
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.