Ontario (ONT) to Seattle (SEA) flights
3 airlines fly nonstop from Ontario (ONT) to Seattle (SEA): Alaska Airlines, Delta Air Lines and Frontier Airlines. The two airports are 957 miles (1,540 km) apart. Alaska Airlines is in oneworld and Delta Air Lines is in SkyTeam. There are also 11 ways to fly it with one stop, through Portland, Sacramento and San Jose and more.
Airlines flying nonstop from ONT to SEA
- Alaska Airlinesoneworld · bookable with 9 programsWho books it
- Delta Air LinesSkyTeam · bookable with 8 programsWho books it
- Frontier AirlinesNot in an allianceWho books it
Book ONT to SEA with points
Loyalty programs that can book at least one of the nonstop airlines, from the Award Booking Guide.
- Aeromexico RewardsBooks Delta Air Lines
- Air France-KLM Flying BlueBooks Delta Air Lines
- Alaska Atmos RewardsBooks Alaska Airlines
- American AAdvantageBooks Alaska Airlines
- British Airways ClubBooks Alaska Airlines
- Cathay Pacific Asia MilesBooks Alaska Airlines
- China Eastern Eastern MilesBooks Delta Air Lines
- Delta SkyMilesBooks Delta Air Lines
- Finnair PlusBooks Alaska Airlines
- Garuda Indonesia GarudaMilesBooks Delta Air Lines
- Iberia ClubBooks Alaska Airlines
- JAL Mileage BankBooks Alaska Airlines
- Korean Air SKYPASSBooks Delta Air Lines
- Qantas Frequent FlyerBooks Alaska Airlines
- Qatar Airways Privilege ClubBooks Alaska Airlines
- SAS EuroBonusBooks Delta Air Lines
- Virgin Atlantic Flying ClubBooks Delta Air Lines
ONT to SEA with one stop
11 connections, most direct first. 2-stop routings and flight times are in Routes with Pro.
- Via Portland (PDX)Alaska Airlines the whole way
- Via Sacramento (SMF)Southwest Airlines the whole way
- Via San Jose (SJC)Southwest Airlines the whole way
- Via Oakland (OAK)Southwest Airlines the whole way
- Via Santa Rosa (STS)Alaska Airlines the whole way
- Via San Francisco (SFO)United Airlines the whole way
- Via Boise (BOI)Alaska Airlines the whole way
- Via Las Vegas (LAS)Southwest Airlines and Frontier Airlines the whole way+2
- Via Salt Lake City (SLC)Delta Air Lines the whole way
- Via Phoenix (PHX)American Airlines and Southwest Airlines the whole way
+1 - Via Denver (DEN)Frontier Airlines, United Airlines and 1 more the whole way+3
ONT to SEA: common questions
Which airlines fly nonstop from ONT to SEA?
Alaska Airlines (oneworld), Delta Air Lines (SkyTeam) and Frontier Airlines fly nonstop from Ontario (ONT) to Seattle (SEA).
How far is Ontario from Seattle by plane?
Ontario (ONT) and Seattle (SEA) are 957 miles (1,540 km) apart along the great circle, the shortest path a flight can take. Connections add distance on top.
Which points programs can book ONT to SEA award flights?
17 programs can book at least one of the nonstop airlines: Aeromexico Rewards, Air France-KLM Flying Blue, Alaska Atmos Rewards, American AAdvantage, British Airways Club, Cathay Pacific Asia Miles, China Eastern Eastern Miles, Delta SkyMiles and 9 more. Which flights each can book depends on its partners, so check the airline before you transfer points.
How many miles does ONT to SEA cost?
It depends on the program: each prices the route from its own chart or dynamically. The Award Flight Pricer compares 30+ programs for ONT to SEA with taxes and fees.
Where can I connect between Ontario and Seattle?
The most direct connections are through Portland (PDX), Sacramento (SMF), San Jose (SJC), Oakland (OAK) and Santa Rosa (STS). On 11 of them the same airline flies both flights, for example Alaska Airlines through Portland.
More routes
Routes are scheduled nonstop flights. The route data is refreshed monthly; this list was last checked November 11, 2026. Seasonal routes and new launches can be missing or end early, so confirm with the airline before you book. Distances are great-circle, the shortest path between the two airports.