Route reliability record

MIA→ATL

Miami to Atlanta

Flights: 6,223
Period: July 2025 to June 2026
Distance: 594 mi
Carriers: 6

This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 6,223 flights, of which Delta Air Lines flew 3,300 at 76.7% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 76.7% on time across 3,300 flights.

On time

73.7%

Arrivals under 15 minutes late, of 6,126 completed flights

Avg delay

80 min

Across delayed arrivals only, not all flights

Cancelled

1.41%

National rate is 1.81%

Best carrier

Delta

76.7% on time across 3,300 flights

These figures cover 6,223 flights between July 2025 and June 2026. Beyond the headline rate, 10.2% 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 MIA to ATL

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 76.7% of the time; American Airlines manages 67.5%. Sample sizes sit next to every figure, because a two-point gap across 1,524 flights means less than a ten-point one.

On-time performance by carrier on MIA to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Envoy Airthin sample	225	78.3%	47 min	1.33%	B
Delta Air Lines	3,300	76.7%	83 min	1.39%	B
Spirit Airlinesthin sample	269	74.4%	71 min	4.09%	C−
Frontier Airlines	861	71.8%	79 min	1.86%	C
American Airlines	1,524	67.5%	82 min	0.79%	C+
Republic Airwaysthin sample	44	65.9%	60 min	0.00%	C+

Delta leads American by 9 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 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,146 flights90.8%
8am–11am1,106 flights85.5%
11am–2pm763 flights77.9%
2pm–5pm1,268 flights65.0%
5pm–8pm1,248 flights59.6%
8pm–5am692 flights63.3%

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

The 5pm–8pm window is where this operation falls apart: 59.6% on time, against 90.8% 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 1,268 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 17 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.October best, July worst

July is the worst month at 61.8% on time, 17 points below October, the best at 78.6%. 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. December was the busiest month here, with 584 flights.

Across the week, Wednesday is the strongest day at 80.1% on time and Sunday the weakest at 63.8%. 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 129,000 reported delay minutes.

Late-arriving aircraft
39%
Carrier
36%
National Airspace System
20%
Extreme weather
4%
Security
0%

39% 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 129,000 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 split is drawn from 129,444 reported delay minutes.

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 46,000 of the 129,000 delay minutes reported here.

Cancellations sit at 1.41% against a national 1.81%, which is ordinary. Diversions add another 0.14%.

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. 10.2% of arrivals land a full hour or more behind schedule, against 8.1% 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 71.0% on time across 6,229 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 6,223 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. October runs 78.6% on time and July 61.8%, a swing of 17 points. If the dates move at all, move them out of July before you think about anything else. 6,126 completed flights over 12 months sit behind that.

Common questions

MIA to ATL questions

How often is MIA to ATL delayed?

About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.3% of the 6,223 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on MIA to ATL?

Delta Air Lines leads at 76.7% on time across 3,300 flights. American Airlines is at the other end on 67.5%, a gap of 9 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 MIA to ATL?

The 5am–8am departure window is the strongest at 90.8% on time. The 5pm–8pm window is the weakest at 59.6%, 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 MIA to ATL?

July is the weakest month at 61.8% on time, compared with 78.6% in October. Across the year that is 17 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. MIA to ATL and ATL to MIA 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