Route reliability record
PDX→DEN
Portland to Denver
- Flights
- 4,280
- Period
- September 2025 to August 2026
- Distance
- 991 mi
- Carriers
- 5
This route lands a B+, 5 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about 55 minutes on average. That rests on 4,280 PDX to DEN flights, of which United Airlines flew 1,820 at 91.2% on time.
Best time to fly PDX to DEN: a 5am–8am departure, ideally on a Sunday. Flights in that window arrived on time 92.3% of the time and Sunday flights 86.7%, against 82.3% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 91.2% on time across 1,820 flights.
Key figures
On time
82.3%
Arrivals under 15 minutes late, of 4,240 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.37%
National rate is 1.89%
Best carrier
United
91.2% on time across 1,820 flights
These figures cover 4,280 flights between September 2025 and August 2026. The median arrival is 6 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.
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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 91.2% of the time; Southwest Airlines manages 73.6%. Sample sizes sit next to every figure, because a two-point gap across 1,548 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,820 | 91.2% | 74 min | 0.49% | A+ |
| Frontier Airlinesthin sample | 256 | 82.1% | 52 min | 0.39% | B+ |
| Alaska Airlines | 643 | 78.6% | 54 min | 0.31% | B+ |
| Southwest Airlines | 1,548 | 73.6% | 48 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.
Flight by flight
Flights on PDX to DEN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Portland to Denver
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. PDX → DENPortland to Denver | United Airlines | 90.8% | 91.2% | 0.49% | 5am–8am, Sun | UA 459 05:00 |
| 2. PDX → DENPortland to Denver | Alaska Airlines | 78.4% | 78.6% | 0.31% | 5am–8am, Tue | — |
| 3. PDX → DENPortland to Denver | Southwest Airlines | 73.4% | 73.6% | 0.26% | 5am–8am, Sun | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 22 points, against 18 points between the best and worst carrier.
- 5am–8am1,128 flights92.3%
- 8am–11am743 flights91.7%
- 11am–2pm930 flights80.0%
- 2pm–5pm932 flights70.8%
- 5pm–8pm518 flights72.4%
- 8pm–5am29 flights—
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.3% of the time, against 70.8% for the afternoon window. That is 22 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 1,128 flights scheduled in it.
Explore
Filter PDX to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On PDX to DEN, the best departure window is 5am–8am at 92.3% on time and the worst is 2pm–5pm at 70.8%, a wide gap of 21.5 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am92.3%
- 8–11am91.7%
- 11am–2pm80.0%
- 2–5pm70.8%
- 5–8pm72.4%
- 8pm–5am—
best all US flightsScale 60% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 17 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.
August is the worst month at 72.9% on time, 17 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 457 flights.
Across the week, Sunday is the strongest day at 86.7% on time and Thursday the weakest at 79.4%, a spread of 7 points.
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 41,000 reported delay minutes.
- 39%Late-arriving aircraft
- 33%National Airspace System
- 27%Carrier
- 1%Extreme weather
- 0%Security
39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 41,000 reported delay minutes here, that single category outweighs weather by 29 to one. The split is drawn from 41,027 reported delay minutes.
33% 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 14,000 minutes out of 41,000, against a national NAS share of 21%.
Cancellations are rare at 0.37%, below the national 1.89% 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
Badly late arrivals are rare here: only 4.8% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
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.
The return leg is a different operation and performs like one: it runs 74.8% on time across 4,280 flights, 8 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 8 points of difference.
The sample behind these figures is 4,280 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.
Work out the risk of missing a connection in DEN after this flight
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 August 72.9%, a swing of 17 points. If the dates move at all, move them out of August before you think about anything else. 4,240 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 six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.7% of the 4,280 flights in this analysis, against 22.7% nationally. Delayed flights are late by about 55 minutes on average.
Which airline is most reliable on PDX to DEN?
United Airlines leads at 91.2% on time across 1,820 flights. Southwest Airlines is at the other end on 73.6%, 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 5am–8am departure window is the strongest at 92.3% on time. The 2pm–5pm window is the weakest at 70.8%, 22 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 August delays on PDX to DEN?
August is the weakest month at 72.9% on time, compared with 90.2% in November. Across the year that is 17 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 PDX to DEN91.2%
- Frontier Airlines on PDX to DEN82.1%
- Alaska Airlines on PDX to DEN78.6%
- Southwest Airlines on PDX to DEN73.6%
- PDX to SEA, a related route84.9%
- PHX to DEN, a related route76.7%
- PDX to LAX, a related route86.6%
- United Airlines on-time record91.2%
- Frontier Airlines on-time record82.1%
- Alaska Airlines on-time record78.6%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.