Route reliability record

PHX→DEN

Phoenix to Denver

Flights: 8,920
Period: July 2025 to June 2026
Distance: 602 mi
Carriers: 6

This route lands a B+, level with the national rate of 77.6%. 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 8,920 flights, of which United Airlines flew 2,370 at 83.5% on time.

United Airlines is the most reliable of the four carriers covered here at 83.5% on time across 2,370 flights.

On time

77.2%

Arrivals under 15 minutes late, of 8,832 completed flights

Avg delay

65 min

Across delayed arrivals only, not all flights

Cancelled

0.70%

National rate is 1.81%

Best carrier

United

83.5% on time across 2,370 flights

These figures cover 8,920 flights between July 2025 and June 2026. The median arrival is 4 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 PHX to DEN

The choice of carrier is not cosmetic here. United Airlines arrives on time 83.5% of the time; Southwest Airlines manages 72.8%. Sample sizes sit next to every figure, because a two-point gap across 3,942 flights means less than a ten-point one.

On-time performance by carrier on PHX to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	2,370	83.5%	75 min	0.59%	B+
Envoy Airthin sample	189	81.8%	53 min	0.53%	B+
Frontier Airlines	1,427	80.0%	88 min	0.63%	B+
American Airlines	974	74.8%	66 min	0.62%	C+
Southwest Airlines	3,942	72.8%	56 min	0.81%	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–8am1,523 flights91.9%
8am–11am1,756 flights84.9%
11am–2pm1,629 flights78.3%
2pm–5pm1,912 flights66.9%
5pm–8pm1,337 flights69.2%
8pm–5am763 flights67.5%

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 91.9% of the time, against 66.9% 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. The 2pm–5pm window is the busiest, with 1,912 flights scheduled in it.

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.

Darker means more delays. Figures are on-time percentages.April best, July worst

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. March was the busiest month here, with 922 flights.

Across the week, Saturday is the strongest day at 81.5% on time and Sunday the weakest at 73.2%. 8 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 47% of the 131,000 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.

Late-arriving aircraft
47%
National Airspace System
27%
Carrier
24%
Extreme weather
2%
Security
0%

47% 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 131,000 reported delay minutes here, that single category outweighs weather by 23 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 131,357 reported delay minutes.

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 91.9% on time here.

Cancellations are rare at 0.70%, 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

7.8% 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 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 75.7% on time across 8,930 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 8,920 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. 8,832 completed flights over 12 months sit behind that.

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 22.8% of the 8,920 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on PHX to DEN?

United Airlines leads at 83.5% on time across 2,370 flights. Southwest Airlines is at the other end on 72.8%, 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 91.9% on time. The 2pm–5pm window is the weakest at 66.9%, 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.

Where to go next

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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures