Route reliability record
PDX→DEN
Portland to Denver
- Flights
- 4,290
- Period
- July 2025 to June 2026
- Distance
- 991 mi
- Carriers
- 5
This route lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 4,290 flights, of which United Airlines flew 1,820 at 90.2% on time.
United Airlines is the most reliable of the three carriers covered here at 90.2% on time across 1,820 flights.
Key figures
On time
80.8%
Arrivals under 15 minutes late, of 4,251 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.44%
National rate is 1.81%
Best carrier
United
90.2% on time across 1,820 flights
These figures cover 4,290 flights between July 2025 and June 2026. The median arrival is 5 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
Which airline is most reliable on PDX to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 90.2% of the time; Southwest Airlines manages 72.2%. Sample sizes sit next to every figure, because a two-point gap across 1,563 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,820 | 90.2% | 71 min | 0.55% | A+ |
| Frontier Airlinesthin sample | 312 | 77.3% | 61 min | 0.96% | B+ |
| Alaska Airlines | 582 | 76.8% | 52 min | 0.34% | B+ |
| Southwest Airlines | 1,563 | 72.2% | 49 min | 0.26% | C+ |
| SkyWest Airlinesthin sample | 13 | 69.2% | 39 min | 0.00% | C+ |
The spread between United and Southwest is 18 points, wide enough that it should decide the booking. On a hundred trips that is 18 more arrivals inside the on-time window.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 points, against 18 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,172 flights89.8%
- 8am–11am738 flights92.1%
- 11am–2pm926 flights78.3%
- 2pm–5pm924 flights68.2%
- 5pm–8pm505 flights71.1%
- 8pm–5am25 flights—
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 92.1% of the time, against 68.2% for the afternoon window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 1,172 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 27 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 63.5% on time, 27 points below November, the best at 90.2%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. July was the busiest month here, with 461 flights.
Across the week, Sunday is the strongest day at 85.8% on time and Thursday the weakest at 78.0%. 8 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 45,000 reported delay minutes.
- 36%Late-arriving aircraft
- 35%National Airspace System
- 27%Carrier
- 2%Extreme weather
- 0%Security
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 45,000 reported delay minutes here, that single category outweighs weather by 21 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 44,945 reported delay minutes.
35% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 16,000 minutes out of 45,000, against a national NAS share of 21%.
Cancellations are rare at 0.44%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here actually costs
5.3% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route are the about an hour kind, which a normal layover absorbs.
The 991 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 73.9% on time across 4,289 flights, 7 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 7 points of difference.
The sample behind these figures is 4,290 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 90.2% on time and July 63.5%, a swing of 27 points. If the dates move at all, move them out of July before you think about anything else. 4,251 completed flights over 12 months sit behind that.
Common questions
PDX to DEN questions
How often is PDX to DEN delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.2% of the 4,290 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on PDX to DEN?
United Airlines leads at 90.2% on time across 1,820 flights. Southwest Airlines is at the other end on 72.2%, a gap of 18 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on PDX to DEN?
The 8am–11am departure window is the strongest at 92.1% on time. The 2pm–5pm window is the weakest at 68.2%, 24 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on PDX to DEN?
July is the weakest month at 63.5% on time, compared with 90.2% in November. Across the year that is 27 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to PDX — the return legseparate record
- Portland International (PDX) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on-time record90.2%
- Frontier Airlines on-time record77.3%
- Alaska Airlines on-time record76.8%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. PDX to DEN and DEN to PDX are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.