Route reliability record

TUS→DEN

Tucson to Denver

Flights: 2,754
Period: July 2025 to June 2026
Distance: 639 mi
Carriers: 4

This route lands a B+, 5 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 2,754 flights, of which SkyWest Airlines flew 621 at 86.5% on time.

SkyWest Airlines is the most reliable of the three carriers covered here at 86.5% on time across 621 flights.

On time

82.9%

Arrivals under 15 minutes late, of 2,731 completed flights

Avg delay

70 min

Across delayed arrivals only, not all flights

Cancelled

0.62%

National rate is 1.81%

Best carrier

SkyWest

86.5% on time across 621 flights

These figures cover 2,754 flights between July 2025 and June 2026. The median arrival is 7 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 TUS to DEN

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 86.5% of the time; Southwest Airlines manages 80.1%. 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 TUS to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	621	86.5%	93 min	0.64%	A+
United Airlines	836	84.7%	73 min	0.60%	B+
Frontier Airlinesthin sample	95	80.9%	52 min	1.05%	B
Southwest Airlines	1,202	80.1%	61 min	0.58%	B+

SkyWest leads Southwest by 6 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 24 points, against 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am776 flights93.1%
8am–11am685 flights87.3%
11am–2pm489 flights79.5%
2pm–5pm638 flights68.8%
5pm–8pm166 flights81.3%
8pm–5am—

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 93.1% of the time, against 68.8% 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 776 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 21 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, July worst

July is the worst month at 69.6% on time, 21 points below November, the best at 90.6%. 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, Saturday is the strongest day at 85.4% on time and Friday the weakest at 81.2%. 4 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 33,000 reported delay minutes.

Carrier
33%
Late-arriving aircraft
31%
National Airspace System
29%
Extreme weather
7%
Security
0%

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 93.1% on time here. The split is drawn from 32,509 reported delay minutes.

No single cause dominates. carrier at 33%, late-arriving aircraft at 31% and national airspace system at 29% split the 33,000 reported delay minutes between them. An even spread like this usually means the operation is running close to its designed capacity with no one obvious weak point, and it is the hardest pattern for a traveller to route around.

Cancellations are rare at 0.62%, 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

6.3% 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 a little over 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 77.1% on time across 2,755 flights, 6 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 6 points of difference.

The sample behind these figures is 2,754 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 90.6% on time and July 69.6%, a swing of 21 points. If the dates move at all, move them out of July before you think about anything else. 2,731 completed flights over 12 months sit behind that.

Common questions

TUS to DEN questions

How often is TUS to DEN delayed?

About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.1% of the 2,754 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on TUS to DEN?

SkyWest Airlines leads at 86.5% on time across 621 flights. Southwest Airlines is at the other end on 80.1%, a gap of 6 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 TUS to DEN?

The 5am–8am departure window is the strongest at 93.1% on time. The 2pm–5pm window is the weakest at 68.8%, 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 TUS to DEN?

July is the weakest month at 69.6% on time, compared with 90.6% in November. Across the year that is 21 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. TUS to DEN and DEN to TUS 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