Route reliability record
ORD→MIA
Chicago to Miami
- Flights
- 4,465
- Period
- September 2025 to August 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, 4 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 4,465 ORD to MIA flights, of which American Airlines flew 3,044 at 74.6% on time.
Best time to fly ORD to MIA: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 87.5% of the time and Tuesday flights 79.3%, against 73.3% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 4 points behind the country as a whole. Across a thousand flights that is about 40 extra late arrivals.
Key figures
On time
73.3%
Arrivals under 15 minutes late, of 4,369 completed flights
Avg delay
74 min
Across delayed arrivals only, not all flights
Cancelled
1.90%
National rate is 1.89%
Best carrier
American
74.6% on time across 3,044 flights
These figures cover 4,465 flights between September 2025 and August 2026. Beyond the headline rate, 9.8% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on ORD to MIA
The two carriers here are closely matched: half a point 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 | 3,044 | 74.6% | 76 min | 1.77% | C |
| United Airlines | 1,088 | 74.4% | 66 min | 0.83% | C+ |
| Frontier Airlinesthin sample | 46 | 64.4% | 120 min | 2.17% | D |
| Spirit Airlinesthin sample | 287 | 56.4% | 71 min | 7.32% | D− |
No carrier stands out. American tops the table at 74.6%, half a point clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on ORD to MIA
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.
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Best ways to make this trip
The most reliable ways to fly Chicago to Miami
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ORD → FLLChicago to Fort Lauderdale | United Airlines | 76.2% | 76.8% | 0.79% | 5am–8am, Tue | UA 1421 07:00 |
| 2. ORD → MIAChicago to Miami | United Airlines | 73.8% | 74.4% | 0.83% | 5am–8am, Tue | — |
| 3. ORD → MIAChicago to Miami | American Airlines | 73.3% | 74.6% | 1.77% | 5am–8am, Wed | AA 2984 05:00 |
| 4. MDW → FLLChicago to Fort Lauderdale | Southwest Airlines | 72.5% | 73.6% | 1.43% | 5am–8am, Wed | — |
| 5. ORD → FLLChicago to Fort Lauderdale | American Airlines | 67.9% | 68.9% | 1.50% | 5am–8am, Tue | — |
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 29 points, against half a point between the best and worst carrier.
- 5am–8am1,308 flights87.5%
- 8am–11am1,194 flights74.3%
- 11am–2pm427 flights70.8%
- 2pm–5pm691 flights63.2%
- 5pm–8pm832 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 87.5% 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. The 5am–8am window is the busiest, with 1,308 flights scheduled in it.
Explore
Filter ORD to MIA 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 ORD to MIA, the best departure window is 5am–8am at 87.5% on time and the worst is 5pm–8pm at 58.9%, a wide gap of 28.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am87.5%
- 8–11am74.3%
- 11am–2pm70.8%
- 2–5pm63.2%
- 5–8pm58.9%
- 8pm–5am—
best all US flightsScale 50% to 95%. Cells under 30 flights show a dash.
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. March was the busiest month here, with 497 flights.
Across the week, Tuesday is the strongest day at 79.3% on time and Sunday the weakest at 64.3%, a spread of 15 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 86,000 reported delay minutes.
- 40%Late-arriving aircraft
- 31%Carrier
- 24%National Airspace System
- 5%Extreme weather
- 0%Security
40% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 86,000 reported delay minutes here, that single category outweighs weather by 8 to one. The split is drawn from 86,284 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 87.5% on time here.
Cancellations sit at 1.90% against a national 1.89%, which is ordinary. Diversions add another 0.25%.
Connections and stage length
What a delay here actually costs
9.8% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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.
The return leg runs 71.1% on time across 4,464 flights, within 2 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 4,465 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 MIA 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. 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. 4,369 completed flights over 12 months sit behind that.
Common questions
ORD to MIA questions
How often is ORD to MIA delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.7% of the 4,465 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on ORD to MIA?
American Airlines leads at 74.6% on time across 3,044 flights. United Airlines is at the other end on 74.4%, a gap of half a point. 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 87.5% on time. The 5pm–8pm window is the weakest at 58.9%, 29 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 ORD to MIA74.6%
- United Airlines on ORD to MIA74.4%
- Spirit Airlines on ORD to MIA56.4%
- ORD to LGA, a related route66.6%
- ATL to MIA, a related route71.2%
- ORD to BOS, a related route66.6%
- American Airlines on-time record74.6%
- United Airlines on-time record74.4%
- Frontier Airlines on-time record64.4%
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
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.
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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.