Carrier route record

DLATL→DEN

Delta Air Lines · Atlanta to Denver

Flights: 2,805
Period: July 2025 to June 2026
Share of route: 50%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on ATL to DEN lands a B, level with the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 2,805 flights. The strongest carrier on the route with a full sample, United Airlines, flew 967 at 85.6% on time.

United Airlines is the most reliable of the three carriers covered here at 85.6% on time across 967 flights.

On time

78.1%

Arrivals under 15 minutes late, of 2,762 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

1.11%

National rate is 1.81%

Whole route

77.6%

Every carrier on ATL to DEN, 5,589 flights

These figures cover 2,805 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

Delta against every carrier on ATL to DEN

Delta flew 2,805 of the 5,589 flights on ATL to DEN, most of the route. Its 78.1% on time is about level with the route as a whole at 77.6%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from United at 85.6% to Frontier at 70.9%.

The choice of carrier is not cosmetic here. United Airlines arrives on time 85.6% of the time; Frontier Airlines manages 70.9%. Sample sizes sit next to every figure, because a two-point gap across 738 flights means less than a ten-point one.

On-time performance by carrier on ATL to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	967	85.6%	78 min	0.41%	A+
Delta Air Lines (this page)	2,805	78.1%	52 min	1.11%	B
Southwest Airlines	1,079	73.4%	54 min	1.11%	C
Frontier Airlines	738	70.9%	82 min	1.36%	C

The spread between United and Frontier is 15 points, wide enough that it should decide the booking. On a hundred trips that is 15 more arrivals inside the on-time window.

Flight by flight

Delta flight numbers on ATL to DEN

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 29 points, against 15 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am133 flights94.0%
8am–11am560 flights86.8%
11am–2pm510 flights86.0%
2pm–5pm562 flights72.8%
5pm–8pm471 flights64.9%
8pm–5am569 flights74.9%

Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 64.9% on time, against 94.0% 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 8pm–5am window is the busiest, with 569 flights scheduled in it.

Across the year

Delta on ATL to DEN through the year

Darker means more delays. Figures are on-time percentages.November best, December worst

December is the weak month at 61.9% on time, against 88.2% in November. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 258 flights.

Across the week, Wednesday is the strongest day at 85.9% on time and Monday the weakest at 73.1%. 13 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

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 31,000 reported delay minutes.

Carrier
40%
National Airspace System
35%
Late-arriving aircraft
20%
Extreme weather
5%

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 12,000 of the 31,000 delay minutes reported here. The split is drawn from 31,360 reported delay minutes.

35% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 11,000 minutes out of 31,000, against a national NAS share of 21%.

Cancellations sit at 1.11% against a national 1.81%, which is ordinary. Diversions add another 0.43%.

Connections and stage length

What a delay here 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 last roughly 50 minutes, 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 86.3% on time across 2,805 flights, 8 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 8 points of difference.

The sample behind these figures is 2,805 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 Delta on ATL to DEN

Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 88.2% on time and December 61.9%, a swing of 26 points. If the dates move at all, move them out of December before you think about anything else. 2,762 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures