Seattle (SEA) to Denver (DEN) flights

United Airlines, Alaska Airlines, Southwest Airlines, Delta Air Lines, Frontier Airlines fly nonstop from Seattle-Tacoma International Airport to Denver International Airport, with about 152 flights a week in July 2026. The 1,024-mile flight takes about 2h 40m gate to gate.

From

SEA

Seattle

Seattle-Tacoma International Airport

DEN

Denver

Denver International Airport

Distance: 1,024 mi · 1,648 km
Flight time: 2h 40m
Airlines: 5
Seats filled: 87%

Flights a week, July 2026

6,269 flights and 906,792 passengers in 12 months

Map data: Natural Earth. Lines follow the shortest (great-circle) path.

Airlines flying SEA to DEN

Airline	Flights a week	Aircraft	Passengers (12 months)	Flight time
United Airlines	46	Boeing 737-800, Airbus A321, Boeing 737-900ER	283,856	2h 38m
Alaska Airlines	38	Boeing 737-900ER, Boeing 737 MAX 9, Boeing 737-800	238,660	2h 41m
Southwest Airlines	34	Boeing 737 MAX 8, Boeing 737-800, Boeing 737-700 / MAX 7	199,518	2h 34m
Delta Air Lines	21	Airbus A220-300, Airbus A220-100, Boeing 737-800	88,362	2h 43m
Frontier Airlines	14	Airbus A321, Airbus A320neo, Airbus A320-100/200	81,270	2h 47m
SkyWest AirlinesSeasonal or ended	n/a	Embraer E175	15,126	2h 47m

Airlines are the operating carrier: regional airlines such as SkyWest or Horizon often fly under a larger airline's brand.

SEA to DEN flight schedule

33 flight numbers flew this route in August 2026, 16 of them almost daily. The first usually leaves at 5:00am and the last at 8:11pm. Times are local and can change; check with the airline before you book.

Flight	Departs	Arrives	Days flown in August 2026	On time (12 months)
UA 2601United Airlines	5:00am	8:45am	31	96%
WN 1384Southwest Airlines	6:30am	10:05am	20	75%
AS 682Alaska Airlines	7:14am	11:04am	13	86%
AS 375Alaska Airlines	8:04am	11:56am	18	90%
DL 1358Delta Air Lines	8:40am	12:26pm	31	81%
UA 1505United Airlines	8:40am	12:32pm	31	91%
WN 1921Southwest Airlines	8:55am	12:35pm	4	n/a
WN 1663Southwest Airlines	10:20am	2:10pm	4	n/a
WN 2860Southwest Airlines	10:45am	2:30pm	20	58%
UA 2031United Airlines	11:03am	2:54pm	18	89%
AS 535Alaska Airlines	11:44am	3:38pm	30	73%
WN 428Southwest Airlines	12:40pm	4:25pm	4	n/a
UA 2832United Airlines	12:44pm	4:35pm	21	61%
AS 304Alaska Airlines	12:48pm	4:36pm	11	60%
UA 1351United Airlines	12:50pm	4:42pm	10	88%
AS 242Alaska Airlines	1:33pm	5:20pm	18	59%
DL 2543Delta Air Lines	1:55pm	5:48pm	31	40%
WN 4507Southwest Airlines	1:55pm	5:45pm	22	19%
F9 3406Frontier Airlines	2:22pm	6:18pm	31	75%
UA 333United Airlines	2:33pm	6:22pm	8	67%
UA 1762United Airlines	2:34pm	6:25pm	15	50%
UA 325United Airlines	3:40pm	7:29pm	10	89%
WN 4697Southwest Airlines	3:45pm	7:30pm	28	52%
UA 757United Airlines	3:54pm	7:45pm	31	85%
AS 602Alaska Airlines	4:26pm	8:10pm	31	75%
WN 196Southwest Airlines	5:40pm	9:25pm	4	n/a
UA 1218United Airlines	6:15pm	9:59pm	19	84%
WN 3485Southwest Airlines	6:15pm	10:00pm	12	87%
WN 2522Southwest Airlines	6:45pm	10:25pm	4	n/a
AS 310Alaska Airlines	7:00pm	10:45pm	31	65%
F9 1176Frontier Airlines	7:06pm	10:58pm	31	78%
DL 2851Delta Air Lines	8:07pm	11:58pm	31	76%
AS 642Alaska Airlines	8:11pm	11:59pm	12	83%

Is SEA to DEN on time?

From September 2025 to August 2026, 78% of 6,333 flights arrived within 15 minutes of schedule and 0.7% were cancelled. Flights leaving around 5am were the most punctual (97%), those around 2pm the least (60%). Most delay time was caused by late-arriving aircraft (36%).

Airline	Flights	On time	Average delay	Cancelled
United Airlines	1,910	88%	9 min	0.6%
Alaska Airlines	1,553	78%	12 min	0.6%
Southwest Airlines	1,342	67%	20 min	0.7%
Delta Air Lines	1,089	76%	15 min	0.8%
Frontier Airlines	439	76%	19 min	0.9%

Airlines as sold: flights operated by regional partners count under the airline on the ticket. Average delay is across all completed flights, early arrivals counted as zero.

On-time arrivals by departure time

Scheduled departure	Flights	On time
5am to 6am	635	97%
7am to 8am	338	86%
8am to 9am	886	86%
9am to 10am	157	90%
10am to 11am	152	76%
11am to 12pm	331	78%
12pm to 1pm	624	78%
1pm to 2pm	615	65%
2pm to 3pm	434	60%
3pm to 4pm	566	78%
4pm to 5pm	179	51%
6pm to 7pm	175	78%
7pm to 8pm	738	75%
8pm to 9pm	298	77%

Flights by month

Month	Flights	Passengers
August 2025	631	102,020
September 2025	573	87,974
October 2025	555	80,747
November 2025	454	61,380
December 2025	461	65,459
January 2026	429	55,463
February 2026	405	52,790
March 2026	444	60,782
April 2026	470	66,161
May 2026	546	76,886
June 2026	627	94,916
July 2026	675	102,384

Source: US Department of Transportation, T-100 Segment data, August 2025 to July 2026.