Route Reliability

Route reliability

Washington (IAD) to Denver (DEN): which airline is most on time?

On-time arrivals, cancellations and long delays for every airline that reported nonstop flights from Washington, VA (IAD) to Denver, CO (DEN), September 2025 to August 2026.

Historical performance Official DOT data through August 2026 · Not live flight status

Washington, VADenver, CO

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Three-letter airport codes, nonstop U.S. domestic flights. One direction at a time.

Route at a glance · September 2025 to August 2026

IAD to DEN

Washington, VA to Denver, CO

On time
82.1%vs 75.6% U.S. average Better than average
Cancelled
0.6%vs 1.9% U.S. average Better than average
60+ min late
5.4%vs 8.1% U.S. average Better than average
Scheduled flights
3,387in 12 months2 airlines
Most reliable airline
United Airlines83.1% on time · 2,791 flights

On time more often than the U.S. average, with fewer cancellations.

Compared with all U.S. flights, September 2025 to August 2026. “About average” means within 1.5 points for on time, 0.3 for cancelled and 1 for 60+ minutes late.

Airlines on this route

Ranked by on-time arrival

Airlines from IAD to DEN, September 2025 to August 2026. Rates are shares of all scheduled flights.
Airline On time Cancelled 60+ min late Avg delay when late Diverted Flights
1. United Airlines Most reliable 83.1% 0.5% 5.6% 68 min 0.7% 2,791
2. Southwest Airlines 77.5% 1.0% 4.5% 48 min 0.2% 596

On time = arrived within 15 minutes of schedule. Avg delay when late = average arrival delay of flights 15+ minutes late. "Most reliable" needs at least 300 flights in 12 months. Tap a heading to sort.

What this means

United Airlines has the strongest record on this route.

  • United Airlines had the best on-time record from Washington (IAD) to Denver (DEN): 83.1% of its 2,791 scheduled flights arrived within 15 minutes of schedule, compared with 77.5% for Southwest Airlines.
  • 0.6% of flights on this route were cancelled (about 1 in 167), 1.3 points lower than the U.S. average of 1.9%.
  • 5.4% of flights, about 1 in 19, arrived an hour or more late. When a flight was late (15+ minutes), the average arrival delay was 63 min.
  • Overall, 82.1% of flights on this route arrived on time, 6.5 points higher than the U.S. average of 75.6%.
  • Over the last 3 years, November was the most reliable month on this route (89.9% on time) and July the least reliable (73.5%).
  • Cancellations peaked in January, when 4.9% of flights were cancelled.
  • Flights scheduled to depart 6 am to 7 am were the most punctual (94.5% on time); flights scheduled to depart 7 pm to 8 pm were the least (66.7%).
  • In the other direction, Denver (DEN) to Washington (IAD), 81.3% of flights were on time and 0.6% were cancelled. Compare airlines DEN to IAD.

Best and worst months to fly IAD to DEN

Jan 77.5%
Feb 81.1%
Mar 85.8%
Apr 80.8%
May 76.6%
Jun 75.1%
Jul 73.5%
Aug 74.3%
Sep 85.5%
Oct 87.4%
Nov 89.9%
Dec 84.3%
Share of scheduled flights on time 12-month average 82.1%
All airlines combined, by calendar month, September 2023 to August 2026 (3 years pooled). Scale starts at zero.
Show as table
PeriodOn timeFlights
January 77.5% 755
February 81.1% 688
March 85.8% 846
April 80.8% 845
May 76.6% 928
June 75.1% 880
July 73.5% 930
August 74.3% 888
September 85.5% 829
October 87.4% 816
November 89.9% 759
December 84.3% 811
Best and worst calendar month by airline, September 2023 to August 2026.
AirlineBest monthWorst month
United Airlines November (90.6%) August (73.9%)
Southwest Airlines November (87.9%) June (67.7%)

Month by month, last 12 months

Sep 84.7%
Oct 83.7%
Nov 90.9%
Dec 76.3%
Jan 83.6%
Feb 82.1%
Mar 80.0%
Apr 87.3%
May 84.2%
Jun 79.8%
Jul 79.3%
Aug 72.4%
Share of scheduled flights on time U.S. average 75.6%
All airlines combined, September 2025 to August 2026. Scale starts at zero.
Show as table
PeriodOn timeFlights
Sep 2025 84.7% 294
Oct 2025 83.7% 283
Nov 2025 90.9% 276
Dec 2025 76.3% 304
Jan 2026 83.6% 280
Feb 2026 82.1% 257
Mar 2026 80.0% 300
Apr 2026 87.3% 291
May 2026 84.2% 316
Jun 2026 79.8% 263
Jul 2026 79.3% 266
Aug 2026 72.4% 257

Best and worst departure times

<6a 89.9%
6a 94.5%
7a 92.9%
8a 86.3%
9a 91.8%
10a 88.6%
12p 90.7%
1p Insufficient sample
2p 81.4%
3p 77.6%
4p 73.8%
5p 68.2%
6p Insufficient sample
7p 66.7%
8p 83.9%
10p 85.3%
Share of scheduled flights on time
By scheduled local departure hour at IAD, September 2025 to August 2026. Hours with no scheduled flights are omitted. Scale starts at zero.
Show as table
PeriodOn timeFlights
Departing before 6 am 89.9% 139
Departing 6 am to 7 am 94.5% 145
Departing 7 am to 8 am 92.9% 70
Departing 8 am to 9 am 86.3% 365
Departing 9 am to 10 am 91.8% 182
Departing 10 am to 11 am 88.6% 211
Departing noon to 1 pm 90.7% 364
Departing 1 pm to 2 pm Insufficient sample 44
Departing 2 pm to 3 pm 81.4% 387
Departing 3 pm to 4 pm 77.6% 170
Departing 4 pm to 5 pm 73.8% 244
Departing 5 pm to 6 pm 68.2% 468
Departing 6 pm to 7 pm Insufficient sample 48
Departing 7 pm to 8 pm 66.7% 153
Departing 8 pm to 9 pm 83.9% 56
Departing 10 pm to 11 pm 85.3% 341
Woman at an airport window watching a plane take off
Photo: Depositphotos (licensed stock, illustrative only). Credits

Sources & data dates

Source
U.S. DOT Bureau of Transportation Statistics, Reporting Carrier On-Time Performance (1987-present)
Period
September 2025 to August 2026 (12 months); month-of-year patterns September 2023 to August 2026
Data through
August 2026
Processed
2026-11-03
Scope
Nonstop scheduled flights from Washington, VA (IAD) to Denver, CO (DEN), one direction. Airlines that report to the DOT only.
Method
Rates use all scheduled flights as the denominator; cancelled and diverted flights count as not on time. Figures based on fewer than 50 scheduled flights are suppressed. Full methodology.

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