Route reliability record

DEN→ATL

Denver to Atlanta

Flights: 5,586
Period: June 2025 to May 2026
Distance: 1,199 mi
Carriers: 4

This route lands a B+, 2 points better than the national rate of 77.4%. 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 5,586 flights, of which Delta Air Lines flew 2,802 at 85.4% on time.

Delta Air Lines is the most reliable of the four carriers covered here at 85.4% on time across 2,802 flights.

On time

79.6%

Arrivals under 15 minutes late, of 5,513 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

0.91%

National rate is 1.80%

Best carrier

Delta

85.4% on time across 2,802 flights

These figures cover 5,586 flights between June 2025 and May 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 85.4% of the time; Southwest Airlines manages 66.8%. Sample sizes sit next to every figure, because a two-point gap across 1,082 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	2,802	85.4%	73 min	1.18%	A
Frontier Airlines	710	78.9%	64 min	0.70%	B+
United Airlines	992	77.4%	65 min	0.40%	B+
Southwest Airlines	1,082	66.8%	55 min	0.83%	C+

The spread between Delta and Southwest is 19 points, wide enough that it should decide the booking. On a hundred trips that is 19 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 19 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am860 flights90.7%
8am–11am1,168 flights82.8%
11am–2pm1,228 flights80.7%
2pm–5pm1,099 flights76.5%
5pm–8pm598 flights60.1%
8pm–5am633 flights80.1%

Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 60.1% on time, against 90.7% 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.

Across the year

When delays peak on this route

This route's year swings by 23 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 67.7% on time, 23 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.

Across the week, Wednesday is the strongest day at 83.4% on time and Sunday the weakest at 76.2%. 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 72,000 reported delay minutes.

Late-arriving aircraft
41%
Carrier
40%
National Airspace System
15%
Extreme weather
4%
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 72,000 reported delay minutes here, that single category outweighs weather by 9 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 largest share of delay minutes, 40%, 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 29,000 of the 72,000 delay minutes reported here.

Cancellations sit at 0.91% against a national 1.80%, which is ordinary. Diversions add another 0.39%.

Connections and stage length

What a delay here actually costs

6.6% 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.

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 is a different operation and performs like one: it runs 76.0% on time across 5,582 flights, 4 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 4 points of difference.

The sample behind these figures is 5,586 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 June 67.7%, a swing of 23 points. If the dates move at all, move them out of June before you think about anything else.

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 20.4% of the 5,586 flights in this analysis, against 22.6% 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 85.4% on time across 2,802 flights. Southwest Airlines is at the other end on 66.8%, a gap of 19 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 90.7% on time. The 5pm–8pm window is the weakest at 60.1%, 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 June delays on DEN to ATL?

June is the weakest month at 67.7% on time, compared with 90.5% in November. Across the year that is 23 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, June 2025 to May 2026. Updated monthly. How this data is collected.

Key figures