Seattle/Tacoma International in September 2025

83.2%departed on time

BTS: A flight is counted as on time if it arrived less than 15 minutes after its scheduled time. Only carriers with at least 0.5 percent of domestic scheduled passenger revenue report.

In September 2025, reporting carriers scheduled 14,552 domestic departures from Seattle/Tacoma International (SEA). 83.2% left less than 15 minutes late and 82.5% reached their destination on time; 0.3% were cancelled.

Nationally that month, 83.1% of flights departed on time and 82.8% arrived on time, so SEA departures were level with the national departure figure.

A year earlier, in September 2024, the airport had 14,805 departures with 81.1% leaving on time: a change of +2.1 points, with flights down 2%.

Flights arriving at SEA that month were on time 83.8% of the time (14,563 scheduled arrivals).

Of the delay minutes that carriers assigned to a BTS cause category that month, air carrier 46%, late-arriving aircraft 27% and national aviation system 24%.

On time 82.5%
Arrived 15+ minutes late 17.0%
Cancelled 0.3%
Diverted 0.2%

Every scheduled departure from SEA in September 2025, judged by arrival at the destination.

September 2025 against a year earlier, the airport's year and the nation

Measure	Sep 2025	Sep 2024	SEA, 12 months to Jul 2026	All reported flights, Sep 2025
Departed on time	83.2%	81.1%	78.2%	83.1%
Arrived on time	82.5%	78.1%	78.6%	82.8%
Cancelled	0.3%	0.3%	0.9%	0.5%
Average departure delay (late minutes only)	9.6 min	10.3 min	13.2 min	12.2 min
Scheduled departures a day	485	494	452	18,748
Scheduled departures	14,552	14,805	164,821	562,439

Airlines that month

Reporting carrier	Flights	Share	On time	Avg arrival delay	Cancelled
AS Alaska Airlines	6,559	45%	81.1%	0.3 min	0.4%
DL Delta Air Lines	2,718	19%	85.4%	1.1 min	0.1%
OO SkyWest Airlines	2,658	18%	87.3%	-3.0 min	0.1%
WN Southwest Airlines	861	6%	68.9%	10.4 min	0.2%
UA United Airlines	831	6%	88.3%	-1.2 min	0.0%
AA American Airlines	547	4%	79.7%	6.4 min	0.9%
HA Hawaiian Airlines	161	1%	69.6%	16.8 min	0.6%
F9 Frontier Airlines	115	1%	73.9%	19.5 min	1.7%
B6 JetBlue Airways	62	0%	79.0%	-1.4 min	1.6%
MQ Envoy Air	40	0%	85.0%	-2.3 min	0.0%

Busiest routes that month

Route	Cities	Flights	On time	Avg arrival delay	Cancelled
SEA–ANC	Seattle to Anchorage	624	88.3%	-6.0 min	0.2%
SEA–LAX	Seattle to Los Angeles	605	88.4%	-2.9 min	0.3%
SEA–SFO	Seattle to San Francisco	584	74.7%	6.6 min	0.7%
SEA–DEN	Seattle to Denver	574	75.6%	6.5 min	0.0%
SEA–PHX	Seattle to Phoenix	545	82.4%	1.2 min	0.7%
SEA–ORD	Seattle to Chicago	509	79.6%	4.3 min	0.0%
SEA–GEG	Seattle to Spokane	462	83.1%	-0.5 min	0.2%
SEA–LAS	Seattle to Las Vegas	440	75.2%	7.4 min	0.0%
SEA–PDX	Seattle to Portland	433	84.1%	-1.3 min	0.0%
SEA–DFW	Seattle to Dallas/Fort Worth	430	79.3%	2.9 min	1.4%
SEA–SLC	Seattle to Salt Lake City	398	88.7%	-4.4 min	0.3%
SEA–SMF	Seattle to Sacramento	398	83.9%	0.2 min	0.3%

By scheduled departure hour

On-time share:under 62%6270768288% and over

Share of departures that left less than 15 minutes late, by scheduled hour (local time), September 2025.

Delay causes

BTS cause category	Share of delay minutes	National, Sep 2025	Minutes
Air carrier	46.2%	34.3%	57,250
Late-arriving aircraft	26.7%	37.4%	33,081
National Aviation System	23.7%	22.6%	29,346
Extreme weather	3.2%	5.6%	3,929
Security	0.2%	0.1%	193

123,799 delay minutes on 2,473 flights that arrived 15 or more minutes late and carried a cause report. Carriers assign the categories; see what each category means.

Questions and answers

How many flights left SEA on time in September 2025?

83.2% of 14,552 scheduled domestic departures left less than 15 minutes late, and 82.5% reached their destination on time. The national figures that month were 83.1% and 82.8%.

How does that compare with a year earlier?

In September 2024, 81.1% of 14,805 departures left on time and 0.3% were cancelled, against 83.2% and 0.3% in September 2025.

Provenance

Source: Bureau of Transportation Statistics, Reporting Carrier On-Time Performance, file for September 2025; public domain. Domestic scheduled flights by reporting carriers, totals and averages only. The site's data runs through July 2026. Full record for SEA · methodology · corrections.