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 (seasonal or thin)


Alaska	STL	SEA	4h 28m	84%	1.0%	781	Flying now
Southwest	STL	SEA	4h 20m	55%	0.0%	103	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 (Seattle is 2 h behind St Louis). Layovers up to 4 hours. Pick a connection for the details.


Alaska Details →	STL 17:37 → PDX 19:47AS 1538	1h 43m Portland	PDX 21:30 → SEA 22:27AS 2421 · flown by Horizon	6h 50m	100%	87%
United Details →	STL 05:10 → DEN 06:32UA 362	1h 29m Denver	DEN 08:01 → SEA 10:00UA 2271	6h 50m	97%	87%
Delta Details →	STL 06:00 → ATL 08:38DL 1524	2h 32m Atlanta	ATL 11:10 → SEA 13:38DL 648	9h 38m	99%	84%
Delta Details →	STL 08:00 → SLC 10:12DL 2363	1h 23m Salt Lake City	SLC 11:35 → SEA 12:52DL 2995	6h 52m	96%	84%
Delta Details →	STL 06:21 → MSP 07:57DL 1597	3h 13m Minneapolis	MSP 11:10 → SEA 12:58DL 889	8h 37m	98%	84%
United Details →	STL 09:20 → ORD 10:52UA 5572 · flown by SkyWest	2h 38m Chicago	ORD 13:30 → SEA 16:09UA 1660	8h 49m	97%	83%
United Details →	STL 09:06 → DEN 10:30UA 2459	3h 30m Denver	DEN 14:00 → SEA 16:00UA 2164	8h 54m	99%	82%
United Details →	STL 06:00 → ORD 07:30UA 2805	1h 15m Chicago	ORD 08:45 → SEA 11:38UA 2099	7h 38m	97%	81%
Tight connection: often missed
Delta Details →	STL 15:57 → MSP 17:40DL 4167 · flown by SkyWest	1h 15m Minneapolis	MSP 18:55 → SEA 20:48DL 881	6h 51m	73%	54%
United Details →	STL 16:48 → DEN 18:23UA 1483	47m Denver	DEN 19:10 → SEA 21:10UA 360	6h 22m	46%	32%
American Details →	STL 17:13 → DFW 19:15AA 2712	58m Dallas-Fort Worth	DFW 20:13 → SEA 22:26AA 2003	7h 13m	30%	15%

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

ATL · 1h 14m · leaves 06:00 3%

CLT · 1h 17m · leaves 05:10 4%

ORD · 1h 04m · leaves 09:08 6%

Afternoon and evening

SFO · 1h 16m · leaves 19:23 56%

DFW · 58m · leaves 17:13 70%

LAS · 50m · leaves 19:40 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 4362 STL 08:15 → SMF Delta DL 4125 SMF 13:00 → SEA Connection details →	2h 45m	9h 01m	100%	93%
Southwest WN 3967 STL 05:45 → PHX Delta DL 2374 PHX 09:20 → SEA Connection details →	2h 25m	8h 50m	100%	90%
Southwest WN 3934 STL 06:00 → LAS Delta DL 2922 LAS 10:59 → SEA Connection details →	3h 34m	9h 51m	100%	89%

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