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 4 in 5 on time.

Nonstops


United	SEA	DEN	2h 47m	89%	0.7%	1,908	Flying now
Alaska	SEA	DEN	2h 48m	79%	0.7%	1,552	Flying now
Frontier	SEA	DEN	2h 59m	78%	1.4%	431	Flying now
Delta	SEA	DEN	2h 52m	77%	0.8%	1,089	Flying now
Southwest	SEA	DEN	2h 40m	70%	0.6%	1,345	Flying now

Best connections, one ticket

Most reliable Quickest (80%+ on time)

Ranked by chance you reach Denver on time. Total trip = scheduled departure to arrival, layover included (Denver is 1 h ahead of Seattle). Layovers up to 4 hours. Pick a connection for the details.


Southwest Details →	SEA 05:00 → SMF 06:50WN 3629	3h 25m Sacramento	SMF 10:15 → DEN 13:35WN 3774	7h 35m	100%	96%
United Details →	SEA 23:49 → IAH 06:10UA 2379	2h 20m Houston	IAH 08:30 → DEN 10:05 +1UA 2816	9h 16m	98%	95%
Alaska Details →	SEA 14:23 → SAN 17:17AS 1432	2h 44m San Diego	SAN 20:01 → DEN 23:30AS 1619	8h 07m	98%	94%
United Details →	SEA 06:00 → LAX 08:44UA 1692	2h 11m Los Angeles	LAX 10:55 → DEN 14:27UA 2061	7h 27m	100%	91%
Delta Details →	SEA 23:59 → MSP 05:17DL 953	1h 43m Minneapolis	MSP 07:00 → DEN 08:06 +1DL 1675	7h 09m	97%	86%
United Details →	SEA 23:11 → ORD 05:18UA 747	1h 47m Chicago	ORD 07:05 → DEN 08:55 +1UA 1217	8h 44m	94%	86%
United Details →	SEA 13:30 → SFO 15:48UA 737	3h 08m San Francisco	SFO 18:56 → DEN 22:44UA 2436	8h 14m	96%	85%
Delta Details →	SEA 07:15 → SLC 10:23DL 2858	2h 57m Salt Lake City	SLC 13:20 → DEN 14:56DL 1623	6h 41m	99%	83%
Tight connection: often missed
United Details →	SEA 15:33 → SFO 17:47UA 2866	1h 09m San Francisco	SFO 18:56 → DEN 22:44UA 2436	6h 11m	62%	54%
United Details →	SEA 07:00 → SFO 09:18UA 1578	1h 22m San Francisco	SFO 10:40 → DEN 14:23UA 1604	6h 23m	55%	37%
Southwest Details →	SEA 10:25 → OAK 12:35WN 1713	50m Oakland	OAK 13:25 → DEN 16:50WN 3043	5h 25m	29%	11%

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

IAH · 1h 12m · leaves 05:00 10%

SFO · 56m · leaves 05:15 16%

Afternoon and evening

ORD · 1h 12m · leaves 10:52 17%

ATL · 1h 00m · leaves 11:56 22%

SFO · 1h 09m · leaves 15:33 38%

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 3629 SEA 05:00 → SMF United UA 2285 SMF 08:50 → DEN Connection details →	2h 00m	6h 16m	100%	97%
Southwest WN 4910 SEA 14:25 → SAN Alaska AS 1619 SAN 20:01 → DEN Connection details →	2h 41m	8h 05m	94%	90%
Alaska AS 696 SEA 13:38 → LAX United UA 2829 LAX 19:45 → DEN Connection details →	3h 20m	8h 37m	100%	90%

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