Denver, CO · departure reliability

DEN

Denver International

Departures: 318,679
Period: June 2025 to May 2026
Carriers: 9
US rank: #2 by volume

Terminal building and aircraft stands at a US airport

Denver

Denver International lands a B+, about a point worse than the national rate of 77.4%. About 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 318,679 flights, of which Delta Air Lines flew 11,605 at 82.4% on time.

Delta Air Lines is the most reliable of the nine carriers covered here at 82.4% on time across 11,605 flights.

On time

76.0%

Departures arriving under 15 minutes late at their destination

Avg delay

66 min

Across delayed flights only

Cancelled

0.82%

National rate is 1.80%

Best carrier

Delta

82.4% on time here

These figures cover 319,000 flights between June 2025 and May 2026. Beyond the headline rate, 8.2% 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 airlines run best out of DEN

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 82.4% of the time; Allegiant Air manages 65.1%. Sample sizes sit next to every figure, because a two-point gap across 413 flights means less than a ten-point one.

On-time performance by carrier departing DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	106,792	78.2%	65 min	0.48%	B+
Southwest Airlines	89,073	69.6%	55 min	0.71%	C+
SkyWest Airlines	75,448	79.4%	79 min	1.19%	B
Frontier Airlines	22,257	77.1%	68 min	0.76%	B+
Delta Air Lines	11,605	82.4%	79 min	1.36%	B
American Airlines	8,855	76.6%	104 min	2.03%	B
Alaska Airlines	2,642	74.3%	58 min	0.87%	C+
JetBlue Airways	1,242	69.0%	91 min	2.66%	C
Allegiant Air	413	65.1%	128 min	1.45%	C

The spread between Delta and Allegiant is 17 points, wide enough that it should decide the booking. On a hundred trips that is 17 more arrivals inside the on-time window.

Route by route

Busiest routes out of DEN

Route-level records vary far more than the airport average. These are the 25 busiest departures from DEN, each with its own on-time rate against the airport-wide 76.0%.

Busiest routes from DEN by flight volume
Route	Flights	On time	Avg delay	Cancelled	Grade
DEN to PHX · Phoenix	8,894	75.4%	67 min	0.88%	B+
DEN to SLC · Salt Lake City	7,765	77.2%	63 min	0.48%	B+
DEN to LAX · Los Angeles	7,728	79.3%	63 min	0.50%	B+
DEN to LAS · Las Vegas	7,066	75.4%	63 min	0.65%	B+
DEN to SEA · Seattle	6,318	73.0%	60 min	0.73%	C+
DEN to ORD · Chicago	6,192	70.4%	85 min	0.99%	C+
DEN to DFW · Dallas-Fort Worth	6,021	74.8%	85 min	1.99%	C
DEN to SAN · San Diego	5,882	75.8%	57 min	0.66%	B+
DEN to MSP · Minneapolis	5,835	77.6%	65 min	0.69%	B+
DEN to ATL · Atlanta	5,586	79.6%	64 min	0.91%	B+
DEN to SFO · San Francisco	5,391	68.1%	61 min	0.54%	C+
DEN to AUS · Austin	5,231	76.2%	62 min	0.57%	B+
DEN to COS · Colorado Springs	5,059	74.9%	71 min	1.54%	C
DEN to LGA · New York	4,673	71.5%	69 min	2.85%	C
DEN to IAH · Houston	4,632	77.9%	65 min	0.30%	B+
DEN to MCO · Orlando	4,582	76.6%	62 min	0.68%	B+
DEN to PDX · Portland	4,297	74.4%	54 min	0.47%	C+
DEN to MCI · Kansas City	4,229	75.1%	60 min	0.40%	B+
DEN to BOS · Boston	3,911	71.6%	69 min	1.15%	C
DEN to SMF · Sacramento	3,832	73.7%	58 min	0.37%	C+
DEN to SNA · Santa Ana	3,708	80.4%	47 min	0.38%	B+
DEN to BNA · Nashville	3,665	74.0%	58 min	0.71%	C+
DEN to STL · St. Louis	3,645	77.9%	60 min	0.27%	B+
DEN to IAD · Washington	3,622	79.1%	62 min	0.72%	B+
DEN to EWR · Newark	3,293	76.4%	81 min	1.55%	B

Departure window

The best time of day to leave DEN

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 25 points, against 17 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am24,868 flights90.3%
8am–11am65,066 flights84.6%
11am–2pm69,954 flights79.9%
2pm–5pm47,741 flights72.8%
5pm–8pm68,710 flights65.8%
8pm–5am42,340 flights68.2%

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

Book the early departure. Flights leaving between 5am–8am arrive on time 90.3% of the time, against 65.8% for the evening 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 DEN runs late

DEN'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.November best, July worst

July is the worst month at 63.0% on time, 22 points below November, the best at 84.7%. 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, Wednesday is the strongest day at 78.7% on time and Friday the weakest at 73.6%. 5 points is a smaller lever than departure hour, but it is free.

Delay causes

Why DEN gets delayed

One category carries most of the weight here. Late-arriving aircraft accounts for 45% of the 4.99 million 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
45%
Carrier
32%
National Airspace System
19%
Extreme weather
4%
Security
0%

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 4.99 million reported delay minutes here, that single category outweighs weather by 11 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 90.3% on time here.

Cancellations are rare at 0.82%, 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.

8.2% 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.

318,679 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.

What to do with this

Flying out of DEN

Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 84.7% on time and July 63.0%, a swing of 22 points. If the dates move at all, move them out of July before you think about anything else.

Common questions

DEN delay questions

How often is Denver (DEN) delayed?

About 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 24.0% of the 318,679 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on Denver (DEN)?

Delta Air Lines leads at 82.4% on time across 11,605 flights. Allegiant Air is at the other end on 65.1%, a gap of 17 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 Denver (DEN)?

The 5am–8am departure window is the strongest at 90.3% on time. The 5pm–8pm window is the weakest at 65.8%, 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 Denver (DEN)?

July is the weakest month at 63.0% on time, compared with 84.7% in November. 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

Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.

Key figures