Route profile
PHL→SEA
Flight reliability, delays and best times to fly from Philadelphia to Seattle, 2,378 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 22% of comparable major US routes (4,598 compared)
Calculated from 3,615 flights. How this is calculated
PHL → SEA arrives on time 69.9% of the time; the return trip, SEA → PHL, arrives on time 75.8% of the time, a 5.9-point gap between the two directions of the same city pair.
PHL → SEA spends 39.3 minutes on the ground on a 2,378-mile trip: 24.7 minutes from pushback to wheels-up at PHL and 14.7 minutes from touchdown to gate at SEA.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
Every airline on this route performs about the same, a narrower carrier gap than 99% of 2,692 comparable routes.
American Airlines (70.1% on time) and Alaska Airlines (69.9%) are close together here.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 2,692 in the comparison.
Why PHL → SEA flights are cancelled
July 2023 – July 2026
PHL → SEA cancelled 59 of 3,615 scheduled flights — about 1 in every 61. The reason filed most often was extreme weather, 59.3% of the cancellations coded on this route — about 1 in every 103 scheduled flights.
Share of cancellations
Of 59 cancelled departures carrying a reason code.
What each reason means
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
35 cancellations, 59.3% of the total.
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
21 cancellations, 35.6% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
3 cancellations, 5.1% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. With only one or two carriers on the route, the split mostly reflects how they file. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
59 coded cancellations were recorded on PHL → SEA; the section appears from 50.
When it goes wrong
July 2023 – July 2026
52 min late
against a median of 2 min early
Percentiles over 3,615 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SEA after arriving from PHL.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 47% | Likely to miss |
| 45 min | 29% | High risk |
| 60 min | 18% | High risk |
| 90 min | 7.8% | Some risk |
| 120 min | 4.4% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.63% of the time and diverts 0.28% of the time, which a late arrival never shows up in.
Chance of missing is the share of 3,546 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 52 minutes late (90th-percentile gate arrival delay), over 3,615 operations.
Any other layover length: connection checker.
Why PHL → SEA runs late
July 2023 – July 2026
airspace and airport capacity, including weather-driven flow control
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for PHL → SEA. Only delays of 15 minutes or more are attributed.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Alaska Airlines | 1,969 | 69.9% | 1.32% | -1 min | 7.6% |
| American Airlines | 1,564 | 70.1% | 2.11% | -2 min | 8.4% |
Alaska Airlines flew 55.7% of the 3,533 flights listed.
Carriers on this route performed within a couple of percentage points of each other.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
| Flight | Scheduled | Operations | On time |
|---|---|---|---|
| AS443 Alaska Airlines | 6:59 PM | 1,078 | 63.2% |
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Friday the least, a gap of 8.1 percentage points.
By month
- Jan: 69.9%
- Feb: 86.3%
- Mar: 70.4%
- Apr: 77.1%
- May: 72.1%
- Jun: 59.6%
- Jul: 62.4%
- Aug: 68.8%
- Sep: 75.9%
- Oct: 72.5%
- Nov: 80.2%
- Dec: 62.3%
June is historically the weakest month and February the strongest, a spread of 26.7 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 62.2% from 124 flights
- August 2023: 79.7% from 124 flights
- September 2023: 79.8% from 120 flights
- October 2023: too few flights to score (97)
- November 2023: too few flights to score (86)
- December 2023: too few flights to score (62)
- January 2024: too few flights to score (59)
- February 2024: too few flights to score (54)
- March 2024: too few flights to score (72)
- April 2024: too few flights to score (85)
- May 2024: too few flights to score (93)
- June 2024: too few flights to score (116)
- July 2024: 63.3% from 123 flights
- August 2024: 61.0% from 124 flights
- September 2024: too few flights to score (92)
- October 2024: too few flights to score (77)
- November 2024: too few flights to score (74)
- December 2024: too few flights to score (86)
- January 2025: too few flights to score (39)
- February 2025: too few flights to score (36)
- March 2025: too few flights to score (71)
- April 2025: too few flights to score (82)
- May 2025: too few flights to score (92)
- June 2025: too few flights to score (116)
- July 2025: 56.8% from 123 flights
- August 2025: 65.7% from 136 flights
- September 2025: 80.3% from 122 flights
- October 2025: 70.2% from 123 flights
- November 2025: too few flights to score (87)
- December 2025: too few flights to score (93)
- January 2026: too few flights to score (68)
- February 2026: too few flights to score (55)
- March 2026: too few flights to score (75)
- April 2026: too few flights to score (114)
- May 2026: 78.2% from 157 flights
- June 2026: 71.6% from 174 flights
- July 2026: 65.7% from 184 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 70.1% against 66.1% in the 12 months before — improving by 4.0 percentage points.
Data and methodology
Calculated by FlyerIntel from 3,615 PHL → SEA flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed