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 82% on time.

Nonstops


United	ONT	DEN	2h 18m	87%	0.4%	823	Flying now
Frontier	ONT	DEN	2h 24m	85%	0.4%	552	Flying now
Southwest	ONT	DEN	2h 15m	77%	0.3%	1,268	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 Ontario). Layovers up to 4 hours. Pick a connection for the details.


Southwest Details →	ONT 06:00 → SMF 07:25WN 3165	2h 50m Sacramento	SMF 10:15 → DEN 13:35WN 3774	6h 35m	98%	94%
Southwest Details →	ONT 05:30 → LAS 06:35WN 3150	2h 20m Las Vegas	LAS 08:55 → DEN 11:50WN 247	5h 20m	100%	88%
United Details →	ONT 13:50 → SFO 15:15UA 1375	3h 41m San Francisco	SFO 18:56 → DEN 22:44UA 2436	7h 54m	97%	86%
United Details →	ONT 05:45 → IAH 11:04UA 1936	1h 29m Houston	IAH 12:33 → DEN 14:17UA 2168	7h 32m	96%	83%
Southwest Details →	ONT 08:00 → PHX 09:15WN 4421	1h 45m Phoenix	PHX 11:00 → DEN 13:45WN 3262	4h 45m	100%	81%
American Details →	ONT 06:11 → PHX 07:30AA 1194	1h 02m Phoenix	PHX 08:32 → DEN 11:29AA 1757	4h 16m	92%	81%
Delta Details →	ONT 06:00 → SLC 08:50DL 2708	1h 25m Salt Lake City	SLC 10:15 → DEN 11:53DL 1553	4h 53m	97%	81%
Delta Details →	ONT 09:40 → SLC 12:28DL 1302	52m Salt Lake City	SLC 13:20 → DEN 14:56DL 1623	4h 16m	96%	80%
Tight connection: often missed
United Details →	ONT 13:50 → SFO 15:15UA 1375	55m San Francisco	SFO 16:10 → DEN 20:01UA 1430	5h 11m	49%	39%
American Details →	ONT 14:15 → DFW 19:30AA 2239	59m Dallas-Fort Worth	DFW 20:29 → DEN 21:32AA 577	6h 17m	55%	25%
United Details →	ONT 18:39 → SFO 20:07UA 5624 · flown by SkyWest	53m San Francisco	SFO 21:00 → DEN 00:47 +1UA 301	5h 08m	11%	10%

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

SFO · 1h 06m · leaves 06:00 6%

MDW · 1h 10m · leaves 23:55 7%

PHX · 1h 02m · leaves 06:11 8%

Afternoon and evening

BNA · 1h 15m · leaves 09:45 22%

DFW · 59m · leaves 14:15 45%

SFO · 53m · leaves 18:39 89%

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 3150 ONT 05:30 → LAS United UA 1315 LAS 09:37 → DEN Connection details →	3h 02m	6h 11m	100%	93%
Southwest WN 3165 ONT 06:00 → SMF United UA 1023 SMF 10:50 → DEN Connection details →	3h 25m	7h 17m	98%	90%
Alaska AS 345 ONT 07:00 → PDX United UA 2793 PDX 11:05 → DEN Connection details →	1h 50m	6h 43m	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