Carrier route record
F9ATL→MIA
Frontier Airlines · Atlanta to Miami
- Flights
- 864
- Period
- July 2025 to June 2026
- Share of route
- 14%
- Carriers
- 6
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.
Frontier on ATL to MIA draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is an hour and a half behind schedule. Build slack into anything you connect to. That rests on 864 flights. The strongest carrier on the route with a full sample, American Airlines, flew 1,527 at 75.2% on time.
The national on-time rate over the same period is 77.6%, so Frontier on ATL to MIA runs 12 points behind the country as a whole. Across a thousand flights that is about 123 extra late arrivals.
Key figures
On time
65.3%
Arrivals under 15 minutes late, of 850 completed flights
Avg delay
91 min
Across delayed arrivals only, not all flights
Cancelled
1.62%
National rate is 1.81%
Whole route
71.0%
Every carrier on ATL to MIA, 6,229 flights
These figures cover 864 flights between July 2025 and June 2026. Beyond the headline rate, 16.8% 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
Frontier against every carrier on ATL to MIA
Frontier flew 864 of the 6,229 flights on ATL to MIA, about 14% of it. Its 65.3% on time is 6 points worse than the route as a whole, which runs 71.0%. Ranked by on-time rate it is number five of six carriers on the route, where the range runs from American at 75.2% to Republic at 63.6%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 5 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 1,527 | 75.2% | 90 min | 0.85% | B+ |
| Envoy Airthin sample | 227 | 74.6% | 76 min | 1.32% | C |
| Spirit Airlinesthin sample | 269 | 73.3% | 99 min | 4.09% | C− |
| Delta Air Lines | 3,298 | 70.3% | 56 min | 1.43% | C |
| Frontier Airlines (this page) | 864 | 65.3% | 91 min | 1.62% | C |
| Republic Airwaysthin sample | 44 | 63.6% | 68 min | 0.00% | D+ |
No carrier stands out. American tops the table at 75.2%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Frontier flight numbers on ATL to MIA
Departure window
When Frontier runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 25 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am23 flights—
- 8am–11am270 flights71.8%
- 11am–2pm93 flights77.4%
- 2pm–5pm160 flights68.8%
- 5pm–8pm54 flights56.0%
- 8pm–5am264 flights52.3%
Scale runs 45% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 52.3% on time, against 77.4% for the 11am–2pm 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 8am–11am window is the busiest, with 270 flights scheduled in it.
Across the year
Frontier on ATL to MIA through the year
July is the worst month at 52.7% on time, 33 points below October, the best at 85.2%. 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. May was the busiest month here, with 93 flights.
Across the week, Wednesday is the strongest day at 75.3% on time and Sunday the weakest at 56.2%. 19 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Frontier runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 59% of the 27,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 59%Late-arriving aircraft
- 29%Carrier
- 11%National Airspace System
- 1%Extreme weather
59% 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 27,000 reported delay minutes here, that single category outweighs weather by 59 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 26,865 reported delay minutes.
Cancellations sit at 1.62% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 16.8% 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 is a different operation and performs like one: it runs 71.8% on time across 861 flights, 7 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 7 points of difference.
One caution: this is a thin sample. 864 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Frontier on ATL to MIA
Put together: treat all of this as provisional. 864 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 65.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 850 completed flights over 12 months sit behind that.
Related
Where to go next
- ATL to MIA, every carrier
- Frontier on MIA to ATL, the return leg
- American Airlines on ATL to MIA75.2%
- Envoy Air on ATL to MIA74.6%
- Spirit Airlines on ATL to MIA73.3%
- Delta Air Lines on ATL to MIA70.3%
- Frontier Airlines network-wide record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Miami International (MIA) delay statistics
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
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.