Route reliability record

DEN→TUS

Denver to Tucson

Flights: 2,755
Period: July 2025 to June 2026
Distance: 639 mi
Carriers: 4

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 2,755 flights, of which SkyWest Airlines flew 622 at 84.3% on time.

SkyWest Airlines is the most reliable of the three carriers covered here at 84.3% on time across 622 flights.

On time

77.1%

Arrivals under 15 minutes late, of 2,741 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.36%

National rate is 1.81%

Best carrier

SkyWest

84.3% on time across 622 flights

These figures cover 2,755 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 DEN to TUS

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 84.3% of the time; Southwest Airlines manages 70.6%. Sample sizes sit next to every figure, because a two-point gap across 1,202 flights means less than a ten-point one.

On-time performance by carrier on DEN to TUS
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	622	84.3%	76 min	0.48%	B+
Frontier Airlinesthin sample	95	81.9%	50 min	1.05%	B
United Airlines	836	80.6%	57 min	0.12%	B+
Southwest Airlines	1,202	70.6%	50 min	0.42%	C+

The spread between SkyWest and Southwest is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 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 26 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am221 flights85.8%
8am–11am414 flights87.3%
11am–2pm613 flights84.7%
2pm–5pm642 flights77.9%
5pm–8pm505 flights66.2%
8pm–5am360 flights61.2%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 61.2% on time, against 87.3% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 2pm–5pm window is the busiest, with 642 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 28 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.November best, June worst

June is the worst month at 61.4% on time, 28 points below November, the best at 89.1%. 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 275 flights.

Across the week, Tuesday is the strongest day at 84.7% on time and Friday the weakest at 72.4%. 12 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 49% of the 35,000 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
49%
Carrier
34%
National Airspace System
14%
Extreme weather
3%
Security
0%

49% 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 35,000 reported delay minutes here, that single category outweighs weather by 18 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 35,097 reported delay minutes.

The largest share of delay minutes, 34%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 12,000 of the 35,000 delay minutes reported here.

Cancellations are rare at 0.36%, 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

7.1% 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 639 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 82.9% on time across 2,754 flights, 6 points above 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 6 points of difference.

The sample behind these figures is 2,755 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 89.1% on time and June 61.4%, a swing of 28 points. If the dates move at all, move them out of June before you think about anything else. 2,741 completed flights over 12 months sit behind that.

Common questions

DEN to TUS questions

How often is DEN to TUS 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 22.9% of the 2,755 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on DEN to TUS?

SkyWest Airlines leads at 84.3% on time across 622 flights. Southwest Airlines is at the other end on 70.6%, a gap of 14 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 DEN to TUS?

The 8am–11am departure window is the strongest at 87.3% on time. The 8pm–5am window is the weakest at 61.2%, 26 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 June delays on DEN to TUS?

June is the weakest month at 61.4% on time, compared with 89.1% in November. Across the year that is 28 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. DEN to TUS and TUS to DEN 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