Route reliability record
ORD→MIA
Chicago to Miami
- Flights
- 4,454
- Period
- June 2025 to May 2026
- Distance
- 1,197 mi
- Carriers
- 4
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, 3 points worse than the national rate of 77.4%. The late ones land about an hour behind schedule. That rests on 4,454 flights, of which American Airlines flew 3,019 at 76.4% on time.
American Airlines is the most reliable of the three carriers covered here at 76.4% on time across 3,019 flights.
Key figures
On time
74.7%
Arrivals under 15 minutes late, of 4,357 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
1.86%
National rate is 1.80%
Best carrier
American
76.4% on time across 3,019 flights
These figures cover 4,454 flights between June 2025 and May 2026. Beyond the headline rate, 8.8% 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
Which airline is most reliable on ORD to MIA
The choice of carrier is not cosmetic here. American Airlines arrives on time 76.4% of the time; Spirit Airlines manages 63.1%. Sample sizes sit next to every figure, because a two-point gap across 378 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 3,019 | 76.4% | 69 min | 1.79% | B |
| United Airlines | 1,011 | 74.4% | 62 min | 0.59% | C+ |
| Frontier Airlinesthin sample | 46 | 64.4% | 120 min | 2.17% | D |
| Spirit Airlines | 378 | 63.1% | 69 min | 5.82% | D− |
Spirit Airlines cancels 5.8% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after 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 30 points, against 13 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,297 flights88.5%
- 8am–11am1,203 flights75.8%
- 11am–2pm517 flights71.2%
- 2pm–5pm664 flights66.2%
- 5pm–8pm760 flights58.9%
- 8pm–5am13 flights—
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 58.9% on time, against 88.5% 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 19 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.
September is the best month on the calendar at 83.1% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back.
Across the week, Tuesday is the strongest day at 81.4% on time and Sunday the weakest at 64.9%. 17 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 75,000 reported delay minutes.
- 36%Late-arriving aircraft
- 30%Carrier
- 28%National Airspace System
- 6%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. That is a cascade, and cascades start small and grow through the day. Across 75,000 reported delay minutes here, that single category outweighs weather by 6 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 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 88.5% on time here.
Cancellations sit at 1.86% against a national 1.80%, which is ordinary. Diversions add another 0.31%.
Connections and stage length
What a delay here actually costs
8.8% of arrivals land an hour or more late, close to the national 8.2%. 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 are the about an hour kind, which a normal layover absorbs.
The 1,197 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 70.8% on time across 4,451 flights, 4 points below 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 4 points of difference.
The sample behind these figures is 4,454 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 83.1% on time and March 64.6%, a swing of 19 points. If the dates move at all, move them out of March before you think about anything else.
Common questions
ORD to MIA questions
How often is ORD to MIA 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 25.3% of the 4,454 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ORD to MIA?
American Airlines leads at 76.4% on time across 3,019 flights. Spirit Airlines is at the other end on 63.1%, a gap of 13 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 ORD to MIA?
The 5am–8am departure window is the strongest at 88.5% on time. The 5pm–8pm window is the weakest at 58.9%, 30 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 March delays on ORD to MIA?
March is the weakest month at 64.6% on time, compared with 83.1% in September. Across the year that is 19 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 ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Miami International (MIA) delay statistics
- American Airlines on-time record76.4%
- United Airlines on-time record74.4%
- Frontier Airlines on-time record64.4%
- 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. ORD to MIA and MIA to ORD 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.