Route reliability record
PHX→DEN
Phoenix to Denver
- Flights
- 8,893
- Period
- June 2025 to May 2026
- Distance
- 602 mi
- Carriers
- 6
This route lands a B+, level with the national rate of 77.4%. Roughly one flight in four 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 8,893 flights, of which United Airlines flew 2,379 at 83.1% on time.
United Airlines is the most reliable of the four carriers covered here at 83.1% on time across 2,379 flights.
Key figures
On time
76.9%
Arrivals under 15 minutes late, of 8,791 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
0.83%
National rate is 1.80%
Best carrier
United
83.1% on time across 2,379 flights
These figures cover 8,893 flights between June 2025 and May 2026. Beyond the headline rate, 8.1% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on PHX to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 83.1% of the time; Southwest Airlines manages 72.6%. Sample sizes sit next to every figure, because a two-point gap across 3,938 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 2,379 | 83.1% | 78 min | 0.63% | B+ |
| Frontier Airlines | 1,394 | 79.9% | 87 min | 0.65% | B+ |
| Envoy Airthin sample | 203 | 78.6% | 60 min | 0.49% | B+ |
| American Airlines | 961 | 74.3% | 65 min | 0.62% | C+ |
| Southwest Airlines | 3,938 | 72.6% | 57 min | 1.09% | C |
| SkyWest Airlinesthin sample | 18 | 66.7% | 98 min | 0.00% | C+ |
United leads Southwest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 25 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,526 flights90.8%
- 8am–11am1,767 flights84.4%
- 11am–2pm1,621 flights78.0%
- 2pm–5pm1,898 flights66.2%
- 5pm–8pm1,312 flights69.8%
- 8pm–5am769 flights67.9%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.8% of the time, against 66.2% for the afternoon window. That is 25 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
Across the year
When delays peak on this route
This route's year swings by 22 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 64.1% on time, 22 points below April, the best at 85.7%. 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.
Across the week, Saturday is the strongest day at 81.9% on time and Sunday the weakest at 72.8%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 45% of the 135,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 45%Late-arriving aircraft
- 29%National Airspace System
- 23%Carrier
- 2%Extreme weather
- 0%Security
45% 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 135,000 reported delay minutes here, that single category outweighs weather by 20 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 practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.8% on time here.
Cancellations are rare at 0.83%, below the national 1.80% 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
8.1% of arrivals land an hour or more late, close to the national 8.2%. 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 602 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 runs 75.4% on time across 8,894 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 8,893 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. April runs 85.7% on time and July 64.1%, a swing of 22 points. If the dates move at all, move them out of July before you think about anything else.
Common questions
PHX to DEN questions
How often is PHX to DEN delayed?
Roughly one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.1% of the 8,893 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on PHX to DEN?
United Airlines leads at 83.1% on time across 2,379 flights. Southwest Airlines is at the other end on 72.6%, a gap of 11 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 PHX to DEN?
The 5am–8am departure window is the strongest at 90.8% on time. The 2pm–5pm window is the weakest at 66.2%, 25 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 PHX to DEN?
July is the weakest month at 64.1% on time, compared with 85.7% in April. Across the year that is 22 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 PHX — the return legseparate record
- Phoenix Sky Harbor International (PHX) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on-time record83.1%
- Frontier Airlines on-time record79.9%
- Envoy Air on-time record78.6%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. PHX to DEN and DEN to PHX 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, June 2025 to May 2026. Updated monthly. How this data is collected.