Route reliability record

DEN→ATL

Denver to Atlanta

Flights: 5,596
Period: July 2025 to June 2026
Distance: 1,199 mi
Carriers: 4

This route lands a B+, 2 points better than the national rate of 77.6%. About one flight in five 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 5,596 flights, of which Delta Air Lines flew 2,805 at 86.3% on time.

Delta Air Lines is the most reliable of the four carriers covered here at 86.3% on time across 2,805 flights.

On time

80.0%

Arrivals under 15 minutes late, of 5,529 completed flights

Avg delay

62 min

Across delayed arrivals only, not all flights

Cancelled

0.86%

National rate is 1.81%

Best carrier

Delta

86.3% on time across 2,805 flights

These figures cover 5,596 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 DEN to ATL

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 86.3% of the time; Southwest Airlines manages 66.3%. Sample sizes sit next to every figure, because a two-point gap across 1,080 flights means less than a ten-point one.

On-time performance by carrier on DEN to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	2,805	86.3%	71 min	1.07%	A
Frontier Airlines	744	78.9%	61 min	0.81%	B+
United Airlines	967	78.0%	64 min	0.31%	B+
Southwest Airlines	1,080	66.3%	54 min	0.83%	C+

The spread between Delta and Southwest is 20 points, wide enough that it should decide the booking. On a hundred trips that is 20 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 31 points, against 20 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am882 flights91.7%
8am–11am1,178 flights82.5%
11am–2pm1,202 flights81.5%
2pm–5pm1,110 flights77.6%
5pm–8pm608 flights61.0%
8pm–5am616 flights79.0%

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

The 5pm–8pm window is where this operation falls apart: 61.0% on time, against 91.7% for the 5am–8am 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 11am–2pm window is the busiest, with 1,202 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 20 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 70.3% on time, 20 points below November, the best at 90.5%. 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. July was the busiest month here, with 525 flights.

Across the week, Tuesday is the strongest day at 83.7% on time and Sunday the weakest at 76.3%. 7 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 69,000 reported delay minutes.

Late-arriving aircraft
41%
Carrier
41%
National Airspace System
14%
Extreme weather
3%
Security
0%

41% 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 69,000 reported delay minutes here, that single category outweighs weather by 13 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 68,821 reported delay minutes.

The largest share of delay minutes, 41%, 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 28,000 of the 69,000 delay minutes reported here.

Cancellations are rare at 0.86%, 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

6.2% 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 1,199 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 77.6% on time across 5,589 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 5,596 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 90.5% on time and July 70.3%, a swing of 20 points. If the dates move at all, move them out of July before you think about anything else. 5,529 completed flights over 12 months sit behind that.

Common questions

DEN to ATL questions

How often is DEN to ATL delayed?

About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 20.0% of the 5,596 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 ATL?

Delta Air Lines leads at 86.3% on time across 2,805 flights. Southwest Airlines is at the other end on 66.3%, a gap of 20 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 ATL?

The 5am–8am departure window is the strongest at 91.7% on time. The 5pm–8pm window is the weakest at 61.0%, 31 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 DEN to ATL?

July is the weakest month at 70.3% on time, compared with 90.5% in November. Across the year that is 20 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 ATL and ATL 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