How long is the flight from ONT to SEA?

Scheduled flights took on average 2 h 46 min from ONT to SEA and 2 h 39 min from SEA to ONT, gate to gate (Aug 2025 – Jul 2026, US BTS). Winds make one direction faster.

Which airlines fly nonstop between ONT and SEA?

Alaska Airlines, SkyWest Airlines, Frontier Airlines, Delta Air Lines flew the route in Aug 2025 – Jul 2026, with 96 flights a week in both directions together.

How much EU261 compensation is a delay on ONT–SEA worth?

Neither EU261 nor UK261 applies: the route neither starts nor ends in the EU, EEA, Switzerland or the UK.

How much is a flight from Ontario, California to Seattle?

Passengers paid $198 on average per one-way trip in Q1 2026, all cabins, taxes included (US DOT).

How much CO2 does a flight from ONT to SEA emit?

About 194 kg CO2e per economy passenger one way, including the extra warming effect of flying high (115 kg without it), using the UK government's 2026 conversion factors.

AirportMiles

Ontario, California (ONT) – Seattle (SEA)

Flights on Google Skyscanner

Distance, flight time and the airlines that fly it, from open data.

Distance: 1,539 km; 956 mi · 831 nm
Flight time: 2 h 46 min / 2 h 39 min; Average gate to gate: ONT → SEA / back
Time difference: none
CO2 per passenger: 194 kg; One way, economy, incl. RF (115 kg CO2 only)
Passengers / year: 541,058; Aug 2025 – Jul 2026 · −7.6%
Flights / week: 96; Both directions, average
Seats filled: 82%; 661,472 seats a year
Airlines nonstop: 4; AS, OO, F9

Traffic: U.S. DOT, Bureau of Transportation Statistics, T-100 Segment (all carriers, scheduled service), Aug 2025 – Jul 2026. Distance: WGS-84 ellipsoid. CO2: UK DESNZ 2026 factors. Sources

Shortest path over the earth's surface (great circle). Real flights bend around weather, winds and airspace.

The way there

Heading from ONT: 347°
Heading from SEA: 163°
Halfway point: 40.78, -119.72
Great-circle km: 1,540 km (sphere, for EU261)
In the air ONT → SEA: 2 h 16 min
In the air SEA → ONT: 2 h 11 min
Clocks: Same time in both

The estimate for a route without real times is 2 h 35 min; how it is worked out is on Sources.

Passengers per month, both directions (Aug 2025 – Jul 2026)Busiest: August 2025: 65,377 passengers

Show as a table

Month	Passengers
Aug 2025	65,377
Sep 2025	48,745
Oct 2025	41,801
Nov 2025	45,527
Dec 2025	45,864
Jan 2026	34,792
Feb 2026	30,479
Mar 2026	36,446
Apr 2026	37,003
May 2026	46,581
Jun 2026	52,021
Jul 2026	56,422

Flights per month, both directions (Aug 2025 – Jul 2026)Busiest: August 2025: 530 flights

Show as a table

Month	Flights
Aug 2025	530
Sep 2025	428
Oct 2025	398
Nov 2025	413
Dec 2025	398
Jan 2026	320
Feb 2026	271
Mar 2026	348
Apr 2026	400
May 2026	496
Jun 2026	473
Jul 2026	509

Airlines flying ONT–SEA nonstop

Airline	Flights / week	Passengers / year	Share of passengers
ASAlaska Airlines	48	352,806	65%
OOSkyWest Airlines	40	129,212	24%
F9Frontier Airlines	6.4	52,612	10%
DLDelta Air Lines	1.3	6,269	1%

Both directions, Aug 2025 – Jul 2026. Airlines with at least one flight a month. U.S. DOT, Bureau of Transportation Statistics, T-100 Segment (all carriers, scheduled service). Sources

Aircraft on this route

Embraer ERJ-175 · 2,090 flights
Boeing 737-900ER · 976 flights
Boeing B737 Max 900 · 899 flights
Boeing 737-800 · 378 flights
Airbus Industrie A321-200n · 156 flights
Airbus Industrie A320-200n · 133 flights
Boeing B737 Max 800 · 131 flights
Boeing 737-700/700LR/Max 7 · 108 flights

Also carried: 374 tonnes of freight and 3 tonnes of mail a year (passenger and cargo flights).

Punctuality

On time: 84.5%; Arrived within 15 min of schedule
Average delay: 10 min; Late arrivals count, early ones as 0
Cancelled: 1.1%
Flights counted: 5,009; Aug 2025 – Jul 2026

Airline	On time	Average delay	Cancelled	Flights
ASAlaska Airlines	79.6%	11 min	1.7%	2,518
OOSkyWest Airlines	90.3%	7 min	0.3%	2,095
F9Frontier Airlines	82.9%	15 min	1.2%	338
DLDelta Air Lines	93.1%	3 min	0%	58

Delay minutes by cause: airline 46% · aircraft arriving late 32% · air traffic system 15% · weather 6% · security 0%.

Both directions, Aug 2025 – Jul 2026. BTS Reporting Carrier On-Time Performance (US domestic flights of the larger US airlines). Sources

What passengers paid

Average fare, Q1 2026: $198; One way, all cabins
Average over a year: $183; Q2 2025 – Q1 2026
Largest airline: Alaska Airlines; 71% of passengers · $193
Lowest-fare airline: Alaska Airlines; 71% of passengers · $193

History, not a price to book: what the average passenger paid per one-way trip in each quarter (Q2 2025 $173 · Q3 2025 $175 · Q4 2025 $194 · Q1 2026 $198).

U.S. DOT Consumer Airfare Report, Table 1a (airline ticket sample, US domestic airport pairs). Sources

Delay compensation (EU261 / UK261)

Measured by great-circle distance: 1,540 km.

Neither EU261 nor UK261 covers this route: it neither starts nor ends in the EU, EEA, Switzerland or the UK. Other countries have their own rules (for example Canada's APPR or Brazil's ANAC rules).

Close to the 1,500 km band edge

This route is within 50 km of 1,500 km, where the amount changes. Airlines and courts measure from the exact airport coordinates — check the figure they use.

Also owed for a cancellation with less than 14 days' notice or denied boarding. Not owed for extraordinary circumstances. On a connection, the distance to the final destination counts. From 23 October 2027 the EU's Regulation 2026/2202 applies; it keeps these amounts (what changes in 2027). Information, not legal advice.

Every airport pair between Ontario, California and Seattle

	SEA	BFI
ONT	1,539	1,547

Kilometres. Linked numbers have a page of their own. All Seattle airports

More routes from ONT

Route	To	Distance	Passengers / year
ONT → DFW	Dallas-Fort Worth, United States	1,912 km	743,327
ONT → DEN	Denver, United States	1,317 km	731,270
ONT → PHX	Phoenix, United States	523 km	685,179
ONT → LAS	Las Vegas, United States	317 km	556,603
ONT → SMF	Sacramento, United States	627 km	394,851
ONT → ATL	Atlanta, United States	3,057 km	304,141
ONT → SFO	San Francisco, United States	585 km	296,329
ONT → TPE	Taoyuan, Taiwan	10,993 km	290,733
ONT → OAK	Oakland, United States	582 km	270,665
ONT → SJC	San Jose, United States	537 km	238,619

More routes from SEA

Route	To	Distance	Passengers / year
SEA → DEN	Denver, United States	1,648 km	1,819,437
SEA → PHX	Phoenix, United States	1,781 km	1,813,338
SEA → LAX	Los Angeles, United States	1,535 km	1,810,795
SEA → ANC	Anchorage, United States	2,331 km	1,694,688
SEA → SFO	San Francisco, United States	1,092 km	1,628,228
SEA → ORD	Chicago, United States	2,769 km	1,622,991
SEA → LAS	Las Vegas, United States	1,394 km	1,596,435
SEA → DFW	Dallas-Fort Worth, United States	2,671 km	1,577,921
SEA → SAN	San Diego, United States	1,690 km	1,233,726
SEA → SLC	Salt Lake City, United States	1,108 km	1,106,553

Questions

Ontario, California (ONT) and Seattle (SEA) are 1,539 km (956 miles, 831 nautical miles) apart, measured along the shortest path over the earth's surface.