Itineraries flown on 20+ days in the Jun 6 – Jul 31, 2026 schedule · each leg’s record Aug 2025 – Jul 2026

No clear winner: airlines and hours on this route all land within a few points of 87% on time.

Nonstops


Delta	ONT	SEA	2h 58m	92%	0.3%	1,076	Flying now
Alaska	ONT	SEA	2h 43m	83%	1.8%	1,260	Flying now
Frontier	ONT	SEA	2h 54m	82%	0.6%	169	Flying now

Best connections, one ticket

Most reliable Quickest (80%+ on time)

Ranked by chance you reach Seattle on time. Total trip = scheduled departure to arrival, layover included. Layovers up to 4 hours. Pick a connection for the details.


Delta Details →	ONT 17:21 → SLC 20:17DL 4443 · flown by SkyWest	2h 28m Salt Lake City	SLC 22:45 → SEA 23:59DL 2998	6h 38m	96%	88%
Alaska Details →	ONT 17:32 → PDX 19:49AS 2456 · flown by Horizon	1h 41m Portland	PDX 21:30 → SEA 22:27AS 2421 · flown by Horizon	4h 55m	98%	87%
Delta Details →	ONT 06:00 → SLC 08:50DL 2708	2h 45m Salt Lake City	SLC 11:35 → SEA 12:52DL 2995	6h 52m	98%	87%
Southwest Details →	ONT 18:30 → SMF 19:55WN 3170	2h 00m Sacramento	SMF 21:55 → SEA 23:50WN 4985	5h 20m	91%	86%
United Details →	ONT 05:00 → DEN 08:20UA 2446	3h 02m Denver	DEN 11:22 → SEA 13:22UA 1424	8h 22m	99%	85%
Alaska Details →	ONT 07:00 → PDX 09:15AS 345	2h 48m Portland	PDX 12:03 → SEA 13:03AS 3078 · flown by SkyWest	6h 03m	100%	85%
Southwest Details →	ONT 08:00 → PHX 09:15WN 4421	1h 30m Phoenix	PHX 10:45 → SEA 13:50WN 814	5h 50m	100%	81%
American Details →	ONT 13:11 → PHX 14:33AA 2244	3h 22m Phoenix	PHX 17:55 → SEA 21:05AA 4307 · flown by Envoy	7h 54m	98%	80%
Tight connection: often missed
United Details →	ONT 13:50 → SFO 15:15UA 1375	1h 12m San Francisco	SFO 16:27 → SEA 18:47UA 2279	4h 57m	67%	51%
Southwest Details →	ONT 20:42 → PHX 21:58WN 3160	47m Phoenix	PHX 22:45 → SEA 01:42 +1WN 3429	5h 01m	30%	16%
United Details →	ONT 18:39 → SFO 20:07UA 5624 · flown by SkyWest	47m San Francisco	SFO 20:54 → SEA 23:19UA 1007	4h 40m	10%	7%

Same layover, different day-part

How often the first flight arrives too late to connect (45 min minimum), for one-ticket layovers of 45–80 minutes.

Morning

DEN · 1h 00m · leaves 05:50 3%

LAS · 1h 05m · leaves 05:30 3%

Afternoon and evening

DFW · 1h 18m · leaves 10:25 7%

PHX · 47m · leaves 20:42 70%

SFO · 47m · leaves 18:39 90%

Delays build through the day, so an afternoon first leg eats the layover. A short connection is fine early in the morning and a gamble later on.

Mixing airlines

One ticketMiss it and the airline rebooks you; bags go through. 45 min is enough.

Separate ticketsMiss it and you buy a new ticket. Re-check bags, clear security again: we require 90 min.


Southwest WN 4421 ONT 08:00 → PHX Delta DL 2419 PHX 12:05 → SEA Connection details →	2h 50m	7h 18m	100%	93%
Southwest WN 383 ONT 06:30 → SJC Delta DL 3736 SJC 11:29 → SEA Connection details →	3h 39m	7h 29m	100%	92%
Alaska AS 345 ONT 07:00 → PDX Delta DL 3818 PDX 11:20 → SEA Connection details →	2h 05m	5h 36m	100%	91%

Rank all connections, any airlines →

Regional partners count as the airline that sells them: SkyWest flying Delta Connection is one Delta ticket.

How these are worked out. Makes the connection: share of the last year’s flights where the first flight arrived with at least 45 minutes to spare (90 on separate tickets). Arrives on time: first flight not cancelled × connection made × second flight not cancelled and arriving within 15 minutes. Not yet counted: the second flight also leaving late (which helps), gate-to-gate distance at the hub, and rebooking after a missed connection.

About this data: US DOT on-time records, Aug 2025 – Jul 2026, all US airlines; regional flights count under the airline that sells them. Schedules (which flights and connections exist, and their times) are as of Jun 6 – Jul 31, 2026; seasonal flights outside that window aren’t ranked. Rebuilt monthly. JSON