Carrier route record

AASEA→PHL

American Airlines · Seattle to Philadelphia

Flights: 619
Period: July 2025 to June 2026
Share of route: 47%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with American Airlines.

American on SEA to PHL lands a B, 6 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 619 flights, with a median arrival 11 minutes early.

Set against the rest of the country, American's SEA to PHL record is 6 points better than the US average of 77.6%. That gap is worth roughly 63 fewer late arrivals for every thousand flights.

On time

83.9%

Arrivals under 15 minutes late, of 603 completed flights

Avg delay

83 min

Across delayed arrivals only, not all flights

Cancelled

2.10%

National rate is 1.81%

Whole route

81.7%

Every carrier on SEA to PHL, 1,326 flights

These figures cover 619 flights between July 2025 and June 2026. The median arrival is 11 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.

Carrier by carrier

American against every carrier on SEA to PHL

American flew 619 of the 1,326 flights on SEA to PHL, about 47% of it. Its 83.9% on time is 2 points better than the route as a whole, which runs 81.7%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from Delta at 84.3% to Alaska at 79.5%. 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.

On-time performance by carrier on SEA to PHL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Linesthin sample	51	84.3%	41 min	0.00%	B+
American Airlines (this page)	619	83.9%	83 min	2.10%	B
Alaska Airlines	656	79.5%	46 min	1.37%	B

Departure window

When American runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 619 flights.

5am–8am69 flights86.4%
8am–11am41 flights90.0%
11am–2pm169 flights83.8%
2pm–5pm—
5pm–8pm—
8pm–5am340 flights82.7%

Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.

The early departures do better, though not dramatically: 90.0% on time for the 8am–11am window against 82.7% for 8pm–5am. Worth taking if the schedule allows, not worth an extra connection. The 8pm–5am window is the busiest, with 340 flights scheduled in it.

Across the year

American on SEA to PHL through the year

Darker means more delays. Figures are on-time percentages.October best, August worst

August is the worst month at 71.2% on time, 22 points below October, the best at 93.4%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. June was the busiest month here, with 87 flights.

Across the week, Monday is the strongest day at 88.4% on time and Sunday the weakest at 77.5%. 11 points is a smaller lever than departure hour, but it is free.

Delay causes

Why American runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 49% of the 8,073 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Late-arriving aircraft
49%
Carrier
25%
Extreme weather
15%
National Airspace System
11%
Security
0%

Extreme weather accounts for 15% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.4 times the usual weather exposure. The split is drawn from 8,073 reported delay minutes.

49% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 8,073 reported delay minutes here, that single category outweighs weather by 3 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit.

Cancellations sit at 2.10% against a national 1.81%, which is ordinary. Diversions add another 0.48%.

Connections and stage length

What a delay here costs

5.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last an hour and a half, which a normal layover absorbs.

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 73.4% on time across 620 flights, 11 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 11 points of difference.

One caution: this is a thin sample. 619 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 American on SEA to PHL

Put together: treat all of this as provisional. 619 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 83.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 603 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures