Which airline is most reliable for SEA (Seattle) to ONT (Ontario)?

The most reliable airline on the SEA to ONT route is Delta Air Lines, with an on-time arrival rate of 90%.

How often are flights delayed from SEA to ONT?

About 17% of flights from SEA to ONT experience delays. 83% arrive on time.

What's the average delay on SEA to ONT flights?

When flights from SEA to ONT are delayed, the average delay is approximately 50 minutes.

Is a short connection safe after a SEA to ONT flight?

With 83% of SEA to ONT flights arriving on time and an average delay of 50 minutes when late, a connection under 60 minutes at ONT is risky. We recommend at least 75-90 minutes for domestic connections after this route.

SEA → ONT

SEA (Seattle) to ONT (Ontario)

SEA (Seattle) to ONT (Ontario) flights arrive on time 83% of the time. The most reliable airline on this route is Delta Air Lines at 90%. The average delay is 50 minutes. Delays on this route are most often caused by the airline (crew, maintenance, or boarding).

Source: Bureau of Transportation Statistics. Updated August 2026.

SEA → ONT on-time performance by month

JanFebMarAprMayJunJulAugSepOctNovDec

Worse

Better

This route is on time most of the time. About 83% of flights arrive on schedule.

Delays on this route are most often caused by the airline (crew, maintenance, or boarding).

Accurate?

Delta Air Lines is significantly more reliable on this route at 90% on time vs Frontier Airlines at 75%.

Airline Comparison

Delta Air Lines leads at 90% on time; Frontier Airlines trails at 75%.

Accurate?

Good to know

Departing from SEA

80% on time

Expect ~21 min sitting on the taxiway after your gate pushes back. SEA has long runway queues.

TSA is currently ~5 min. Best time: 4 AM (about 5 min).

More about SEA →

Arriving at ONT

82% on time

When flights into ONT are late, the average delay is 64 minutes. Build buffer if you have ground plans.

If connecting at ONT: TSA is ~5 min right now. Allow at least 60 minutes for a domestic connection.

More about ONT →Connection times at ONT →

Flight cancelled or delayed?

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SEA Airport ONT Airport

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Data last updated August 2026. Source: Bureau of Transportation Statistics.