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Route · ONT → SEA · 2020–2025 BTS data

Ontario to Seattle

According to PlainFlights' route traffic ranking (BTS On-Time Performance total flights), ONT to SEA (Ontario to Seattle) ranks #816 of 4927 tracked domestic routes by total flights (most flights = #1).

Data updated 2026-06-13

87.1%
On-time
+8.1 pts
vs US avg
69 min
Delay when late
12,860
Flights
#816 of 4927
Corpus placement

Cancelled

1.2%

Best Month

Oct 2024 94%

Worst Month

Feb 2025 81%

Distance

956 mi

Carriers

17

Monthly Performance

Recent 24 months of route data.

Period Flights Delayed Cancelled Diverted Carriers
Dec 2025 200 36 2 1 F9,AS,OO
Nov 2025 211 26 7 0 OO,F9,AS
Oct 2025 200 30 2 0 AS,OO,F9
Sep 2025 213 25 1 1 OO,DL,F9,AS
Aug 2025 266 43 2 0 OO,F9,AS,DL
Jul 2025 302 54 9 0 AS,OO,F9
Jun 2025 266 39 1 0 AS,OO,F9
May 2025 258 39 2 1 AS,OO,F9
Apr 2025 202 19 0 0 F9,OO,AS
Mar 2025 183 26 0 2 AS,OO,F9
Feb 2025 147 28 4 0 AS,OO,F9
Jan 2025 166 31 3 1 AS,OO,F9
Dec 2024 174 23 1 2 AS,F9,OO
Nov 2024 227 22 1 0 OO,AS,F9
Oct 2024 209 12 0 0 AS,OO,F9
Sep 2024 224 40 0 0 OO,AS,F9
Aug 2024 255 42 3 0 AS,F9,OO
Jul 2024 276 48 3 0 AS,F9,OO
Jun 2024 270 51 1 0 AS,F9,OO
May 2024 254 35 1 0 AS,F9,OO
Apr 2024 200 14 0 0 AS,DL,OO
Mar 2024 152 15 0 0 AS,DL
Feb 2024 133 10 0 0 AS,DL
Jan 2024 143 10 17 0 AS,DL

ONT–SEA seasonal on-time pattern

Best: March (89.7%) · weakest: June (84.1%)

82%84%86%88%90% JanFebMarAprMayJunJulAugSepOctNovDec 85.1%

Strongest calendar month

March

89.7% on-time · ~170 flights/mo

Busiest calendar month

August

~227 flights/mo avg

Weakest calendar month

June

84.1% on-time · ~226 flights/mo

Cancellation Rate

1.2%

60 of 5,131 flights

Diversion Rate

0.2%

8 of 5,131 flights

Explore origin & destination

On-time and delay data for the airports this route connects.

ONT - Ontario

Full on-time, delay-cause, and seasonal performance for Ontario, CA.

ONT on-time profile

SEA - Seattle

Full on-time, delay-cause, and seasonal performance for Seattle, WA.

SEA on-time profile

Compare the two airports

See ONT and SEA side by side on delays, cancellations, and reliability.

Compare ONT vs SEA

Origin-hub reliability standing

Among ONT's stronger departures

ONT → SEA posts a 87.1% on-time rate, landing in the ≥85% band with 10 of 21 BTS-tracked routes leaving Ontario. The same hub also shows 9 mid-band and 2 challenged departures · fleet-wide on-time rank #617 of 4927 (highest on-time = #1).

What the Data Says About ONT to SEA

Ontario to Seattle (ONT to SEA) is one of the more dependable pairings in the BTS On-Time Performance dataset: a 87.1% on-time rate across 12,860 flights, with delays that do happen averaging 69.4 minutes. The corridor runs roughly 956 miles and is served by 17 carriers. Over the most recent 24 months, 60 of 5,131 flights were cancelled (1.2%) and 8 diverted (0.2%).

Monthly performance varies moderately here: Oct 2024 was the strongest month at 94% on-time versus Feb 2025 at 81%, a 13-point difference.

On the multi-year calendar, ONT–SEA peaks in March at 89.7% on-time while August carries the heaviest traffic (~227 flights per month) ; the softest month is June at 84.1%, a 5.6-point swing that repeats because the corridor's weather and holiday mix stays stable year to year.

Frequently Asked Questions

Where does ONT to SEA rank among US routes by traffic? ▼
According to PlainFlights' route traffic ranking, ONT to SEA ranks #816 of 4927 tracked domestic routes by total flights (most flights = #1). That ordinal matches our busiest-routes listing (total_flights DESC). See /methodology#corpus-placement for the exact sort basis.
How often are flights delayed from ONT to SEA? ▼
Flights from Ontario to Seattle have a 87.1% on-time rate based on 12,860 flights. The average delay is 69.4 minutes. The best recent month was Oct 2024 with 94% on-time.
What is the cancellation rate for ONT to SEA? ▼
Over the last 24 months, 1.2% of flights on this route were cancelled (60 of 5,131 flights) and 0.2% were diverted.
How far is the flight from ONT to SEA? ▼
The flight distance from Ontario (ONT) to Seattle (SEA) is approximately 956 miles. This route is served by 17 carriers.
When is the best time to fly from ONT to SEA? ▼
The best recent month for on-time performance was Oct 2024 (94% on-time). The worst was Feb 2025 (81% on-time). Consider booking during months with historically better performance.

Airports on this route

ONT Airport

Ontario
SEA Airport

Seattle
Data source

Data Source: Bureau of Transportation Statistics (BTS), On-Time Performance Data. Statistics reflect cumulative performance across all available reporting periods.

Read our methodology - how this data is sourced, computed, and verified.

Using ONT–SEA data

ONT–SEA runs 8.1 pts above the national 79% average; the remaining risk is month-to-month swing and carrier mix, not a weak headline rate.

  • Compare ONT and SEA airport profiles: delay causes and top routes differ even on the same corridor. ONT airport
  • If your dates flex, March (89.7% on-time) beats June (84.1%) on this corridor. Seasonal chart
  • 4 other routes post a similar 87.1% on-time rate; compare before you commit to this pairing. Similar routes

On-time rate reflects the BTS historical average across all reporting carriers on this origin–destination pair, not any single flight or booking recommendation.

Data sourced from U.S. Department of Transportation Bureau of Transportation Statistics (BTS) On-Time Performance data. See our methodology for details. Retrieved and formatted by PlainFlights

Every figure on PlainFlights is rendered directly from BTS On-Time Performance data, no number is typed in by an editor. This page aggregates this specific route's on-time performance and monthly trend, live from the dataset. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.