Route reliability record
ATL→DEN
Atlanta to Denver
- Flights
- 5,594
- Period
- September 2025 to August 2026
- Distance
- 1,199 mi
- Carriers
- 4
This route lands a B, level with the national rate of 77.3%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 5,594 ATL to DEN flights, of which United Airlines flew 923 at 85.9% on time.
Best time to fly ATL to DEN: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 88.1% of the time and Wednesday flights 84.1%, against 78.0% for the route overall.
United Airlines is the most reliable of the four carriers covered here at 85.9% on time across 923 flights.
Key figures
On time
78.0%
Arrivals under 15 minutes late, of 5,513 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
1.11%
National rate is 1.89%
Best carrier
United
85.9% on time across 923 flights
These figures cover 5,594 flights between September 2025 and August 2026. The median arrival is 5 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.
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Carrier by carrier
Which airline is most reliable on ATL to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 85.9% of the time; Frontier Airlines manages 71.2%. Sample sizes sit next to every figure, because a two-point gap across 793 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 923 | 85.9% | 84 min | 0.43% | A+ |
| Delta Air Lines | 2,807 | 79.0% | 52 min | 1.21% | B |
| Southwest Airlines | 1,071 | 73.5% | 57 min | 1.21% | C |
| Frontier Airlines | 793 | 71.2% | 79 min | 1.39% | 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
Flights on ATL to DEN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
- Delta 51916:3566.7% · 365 flights
- United 23516:3578.5% · 363 flights
- Delta 74618:5967.8% · 361 flights
- Delta 70612:1584.7% · 360 flights
- Frontier 329312:3381.2% · 355 flights
- Delta 53013:5580.5% · 323 flights
- United 34009:0091.1% · 286 flights
- Delta 95622:5975.4% · 283 flights
- Delta 49320:5477.2% · 269 flights
- Frontier 359920:4060.7% · 259 flights
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Best ways to make this trip
The most reliable ways to fly Atlanta to Denver
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ATL → DENAtlanta to Denver | United Airlines | 85.5% | 85.9% | 0.43% | 5am–8am, Wed | UA 340 09:00 |
| 2. ATL → DENAtlanta to Denver | Delta Air Lines | 78.0% | 79.0% | 1.21% | 5am–8am, Wed | DL 706 12:15 |
| 3. ATL → DENAtlanta to Denver | Southwest Airlines | 72.6% | 73.5% | 1.21% | 5am–8am, Tue | — |
| 4. ATL → DENAtlanta to Denver | Frontier Airlines | 70.2% | 71.2% | 1.39% | 11am–2pm, Thu | F9 3293 12:33 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 26 points, against 15 points between the best and worst carrier.
- 5am–8am687 flights88.1%
- 8am–11am1,102 flights86.5%
- 11am–2pm996 flights85.3%
- 2pm–5pm1,138 flights74.0%
- 5pm–8pm768 flights61.9%
- 8pm–5am903 flights70.5%
Scale runs 55% to 95%.
The 5pm–8pm window is where this operation falls apart: 61.9% on time, against 88.1% 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 2pm–5pm window is the busiest, with 1,138 flights scheduled in it.
Explore
Filter ATL to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On ATL to DEN, the best departure window is 5am–8am at 88.1% on time and the worst is 5pm–8pm at 61.9%, a wide gap of 26.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am88.1%
- 8–11am86.5%
- 11am–2pm85.3%
- 2–5pm74.0%
- 5–8pm61.9%
- 8pm–5am70.5%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route's year swings by 18 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.
December is the weak month at 68.2% on time, against 86.5% 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 532 flights.
Across the week, Wednesday is the strongest day at 84.1% on time and Sunday the weakest at 71.3%, a spread of 13 points.
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 74,000 reported delay minutes.
- 36%Late-arriving aircraft
- 33%Carrier
- 27%National Airspace System
- 4%Extreme weather
- 0%Security
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 74,000 reported delay minutes here, that single category outweighs weather by 10 to one. The split is drawn from 74,478 reported delay minutes.
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 88.1% on time here.
Cancellations sit at 1.11% against a national 1.89%, which is ordinary. Diversions add another 0.34%.
Connections and stage length
What a delay here actually costs
7.3% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, 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.
The return leg runs 78.6% on time across 5,603 flights, within half a point 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 5,594 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.
Work out the risk of missing a connection in DEN after this flight
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 86.5% on time and December 68.2%, a swing of 18 points. If the dates move at all, move them out of December before you think about anything else. 5,513 completed flights over 12 months sit behind that.
Common questions
ATL to DEN questions
How often is ATL to DEN delayed?
Roughly one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.0% of the 5,594 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ATL to DEN?
United Airlines leads at 85.9% on time across 923 flights. Frontier Airlines is at the other end on 71.2%, a gap of 15 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 ATL to DEN?
The 5am–8am departure window is the strongest at 88.1% on time. The 5pm–8pm window is the weakest at 61.9%, 26 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 December delays on ATL to DEN?
December is the weakest month at 68.2% on time, compared with 86.5% in November. Across the year that is 18 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on ATL to DEN85.9%
- Delta Air Lines on ATL to DEN79.0%
- Southwest Airlines on ATL to DEN73.5%
- Frontier Airlines on ATL to DEN71.2%
- ATL to LGA, a related route72.3%
- PHX to DEN, a related route76.7%
- ATL to MCO, a related route70.3%
- United Airlines on-time record85.9%
- Delta Air Lines on-time record79.0%
- Southwest Airlines on-time record73.5%
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
Direction matters. ATL to DEN and DEN to ATL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.