Route reliability record
ATL→MIA
Atlanta to Miami
- Flights
- 6,245
- Period
- June 2025 to May 2026
- Distance
- 594 mi
- Carriers
- 6
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.4%. The late ones land a little over an hour behind schedule. That rests on 6,245 flights, of which American Airlines flew 1,547 at 75.2% on time.
American Airlines is the most reliable of the three carriers covered here at 75.2% on time across 1,547 flights.
Key figures
On time
69.7%
Arrivals under 15 minutes late, of 6,132 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
1.52%
National rate is 1.80%
Best carrier
American
75.2% on time across 1,547 flights
These figures cover 6,245 flights between June 2025 and May 2026. Beyond the headline rate, 11.0% 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 airline is most reliable on ATL to MIA
The choice of carrier is not cosmetic here. American Airlines arrives on time 75.2% of the time; Frontier Airlines manages 63.8%. Sample sizes sit next to every figure, because a two-point gap across 826 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 1,547 | 75.2% | 91 min | 1.10% | B |
| Envoy Airthin sample | 230 | 74.9% | 76 min | 1.30% | C |
| Spirit Airlinesthin sample | 287 | 71.7% | 91 min | 3.83% | C− |
| Delta Air Lines | 3,311 | 68.1% | 57 min | 1.51% | C |
| Frontier Airlines | 826 | 63.8% | 90 min | 1.69% | D |
| Republic Airwaysthin sample | 44 | 63.6% | 68 min | 0.00% | D+ |
American leads Frontier by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am861 flights88.0%
- 8am–11am1,358 flights77.1%
- 11am–2pm1,135 flights75.3%
- 2pm–5pm1,042 flights58.6%
- 5pm–8pm910 flights57.0%
- 8pm–5am939 flights59.9%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 57.0% on time, against 88.0% 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.
Across the year
When delays peak on this route
This route'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.
July is the worst month at 58.4% on time, 22 points below September, the best at 80.1%. 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 77.5% on time and Sunday the weakest at 61.4%. 16 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 133,000 reported delay minutes.
- 38%Late-arriving aircraft
- 36%Carrier
- 21%National Airspace System
- 5%Extreme weather
- 0%Security
38% 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 133,000 reported delay minutes here, that single category outweighs weather by 8 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, 36%, 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 48,000 of the 133,000 delay minutes reported here.
Cancellations sit at 1.52% against a national 1.80%, which is ordinary. Diversions add another 0.29%.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.0% of arrivals land a full hour or more behind schedule, against 8.2% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The 594 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 72.6% on time across 6,240 flights, within 3 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 6,245 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. September runs 80.1% on time and July 58.4%, a swing of 22 points. If the dates move at all, move them out of July before you think about anything else.
Common questions
ATL to MIA questions
How often is ATL to MIA delayed?
Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 30.3% of the 6,245 flights in this analysis, against 22.6% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on ATL to MIA?
American Airlines leads at 75.2% on time across 1,547 flights. Frontier Airlines is at the other end on 63.8%, a gap of 11 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 MIA?
The 5am–8am departure window is the strongest at 88.0% on time. The 5pm–8pm window is the weakest at 57.0%, 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 ATL to MIA?
July is the weakest month at 58.4% on time, compared with 80.1% in September. 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.
Related
Where to go next
- MIA to ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Miami International (MIA) delay statistics
- American Airlines on-time record75.2%
- Envoy Air on-time record74.9%
- Spirit Airlines on-time record71.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. ATL to MIA and MIA to ATL 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.