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Route · SEA → ONT · 2020–2025 BTS data

Seattle to Ontario

According to PlainFlights' route traffic ranking (BTS On-Time Performance total flights), SEA to ONT (Seattle to Ontario) ranks #815 of 4927 tracked domestic routes by total flights (most flights = #1).

Data updated 2026-06-13

83.5%
On-time
+4.5 pts
vs US avg
57 min
Delay when late
12,866
Flights
#815 of 4927
Corpus placement

Cancelled

1.2%

Best Month

Sep 2025 91%

Worst Month

Dec 2025 73%

Distance

956 mi

Carriers

17

Monthly Performance

Recent 24 months of route data.

Period Flights Delayed Cancelled Diverted Carriers
Dec 2025 200 55 2 0 F9,AS,OO
Nov 2025 211 35 7 0 OO,F9,AS
Oct 2025 200 24 2 0 AS,OO,F9
Sep 2025 213 19 0 0 OO,DL,F9,AS
Aug 2025 266 59 1 0 OO,F9,AS,DL
Jul 2025 302 81 10 0 AS,OO,F9
Jun 2025 267 64 2 0 AS,OO,F9
May 2025 258 38 2 0 AS,OO,F9
Apr 2025 202 20 0 0 F9,OO,AS
Mar 2025 183 29 0 0 AS,OO,F9
Feb 2025 147 38 6 0 AS,OO,F9
Jan 2025 167 25 1 8 AS,OO,F9
Dec 2024 175 24 1 1 AS,F9,OO
Nov 2024 226 29 1 0 OO,AS,F9
Oct 2024 209 21 0 0 AS,OO,F9
Sep 2024 224 40 1 1 OO,AS,F9
Aug 2024 256 47 3 0 AS,F9,OO
Jul 2024 276 48 4 0 AS,F9,OO
Jun 2024 270 56 2 0 AS,F9,OO
May 2024 254 43 0 0 AS,F9,OO
Apr 2024 200 36 0 0 AS,DL,OO
Mar 2024 152 29 0 0 AS,DL
Feb 2024 133 21 0 1 AS,DL
Jan 2024 143 23 15 0 AS,DL

SEA–ONT seasonal on-time pattern

Best: October (87.9%) · weakest: July (79.2%)

78%80%82%84%86%88%90% JanFebMarAprMayJunJulAugSepOctNovDec 80.9%

Strongest calendar month

October

87.9% on-time · ~199 flights/mo

Busiest calendar month

August

~227 flights/mo avg

Weakest calendar month

July

79.2% on-time · ~200 flights/mo

Cancellation Rate

1.2%

60 of 5,134 flights

Diversion Rate

0.2%

11 of 5,134 flights

Explore origin & destination

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

SEA - Seattle

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

SEA on-time profile

ONT - Ontario

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

ONT on-time profile

Compare the two airports

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

Compare SEA vs ONT

Origin-hub reliability standing

Mid-pack among SEA departures

From SEA, this corridor sits with 63 other 75–85% on-time routes out of 89 tracked departures, not the hub's reliability leaders (25 at ≥85%) and not the softest ( 1 below 75%). Destination: Ontario · fleet on-time rank #1768 of 4927.

What the Data Says About SEA to ONT

Bureau of Transportation Statistics records show Seattle to Ontario (SEA to ONT) running a 83.5% on-time rate over 12,866 tracked flights, on the stronger end of a typical domestic pairing. When flights do run late, the average delay is 57.0 minutes. The 956-mile corridor is served by 17 carriers, and over the last 24 months 1.2% of 5,134 flights were cancelled, 0.2% diverted.

The monthly split is wide on this route: Sep 2025 posted the strongest performance at 91% on-time, while Dec 2025 came in at just 73% - a 19-point swing worth factoring into travel timing.

On the multi-year calendar, SEA–ONT peaks in October at 87.9% on-time while August carries the heaviest traffic (~227 flights per month) ; the softest month is July at 79.2%, a 8.7-point swing that repeats because the corridor's weather and holiday mix stays stable year to year.

Frequently Asked Questions

Where does SEA to ONT rank among US routes by traffic? ▼
According to PlainFlights' route traffic ranking, SEA to ONT ranks #815 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 SEA to ONT? ▼
Flights from Seattle to Ontario have a 83.5% on-time rate based on 12,866 flights. The average delay is 57.0 minutes. The best recent month was Sep 2025 with 91% on-time.
What is the cancellation rate for SEA to ONT? ▼
Over the last 24 months, 1.2% of flights on this route were cancelled (60 of 5,134 flights) and 0.2% were diverted.
How far is the flight from SEA to ONT? ▼
The flight distance from Seattle (SEA) to Ontario (ONT) is approximately 956 miles. This route is served by 17 carriers.
When is the best time to fly from SEA to ONT? ▼
The best recent month for on-time performance was Sep 2025 (91% on-time). The worst was Dec 2025 (73% on-time). Consider booking during months with historically better performance.

Airports on this route

SEA Airport

Seattle
ONT Airport

Ontario
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 SEA–ONT data

SEA–ONT runs 4.5 pts above the national 79% average; the remaining risk is month-to-month swing and carrier mix, not a weak headline rate.

  • Compare SEA and ONT airport profiles: delay causes and top routes differ even on the same corridor. SEA airport
  • If your dates flex, October (87.9% on-time) beats July (79.2%) on this corridor. Seasonal chart
  • 4 other routes post a similar 83.5% 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.