Route reliability record
MIA→ORD
Miami to Chicago
- Flights
- 85,152
- Period
- June 2025 to May 2026
- Distance
- 1,199 mi
- Carriers
- 2
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, 5 points worse than the national rate of 75.9%. The late ones land roughly 55 minutes behind schedule. That rests on 85,152 flights, of which Delta Air Lines flew 13,705 at 81.6% on time.
The national on-time rate over the same period is 75.9%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 52 extra late arrivals.
Key figures
On time
70.7%
Arrivals under 15 minutes late, of 82,687 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
2.67%
National rate is 2.23%
Best carrier
Delta
81.6% on time across 13,705 flights
These figures cover 85,000 flights between June 2025 and May 2026. Beyond the headline rate, 11.1% 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 ORD
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.6% of the time; Frontier Airlines manages 68.6%. Sample sizes sit next to every figure, because a two-point gap across 71,447 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 13,705 | 81.6% | 52 min | 1.03% | B |
| Frontier Airlines | 71,447 | 68.6% | 62 min | 2.98% | C |
The spread between Delta and Frontier is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
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 18 points, against 13 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am13,198 flights80.2%
- 8am–11am17,457 flights75.2%
- 11am–2pm15,753 flights71.2%
- 2pm–5pm14,901 flights66.7%
- 5pm–8pm15,327 flights62.2%
- 8pm–5am8,515 flights68.7%
Scale runs 55% to 85%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 62.2% on time, against 80.2% 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
Twelve months, one bar each, drawn from the same 85,152 flights. The strip shows how much of this route's record is set by the calendar rather than by the operation.
January is the weak month at 63.7% on time, against 74.7% in May. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days.
The day of the week is close to irrelevant here: 2 points separates the best day from the worst. Weekly demand peaks are not what drives the delays on this operation.
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 1.27 million reported delay minutes.
- 40%Late-arriving aircraft
- 28%National Airspace System
- 26%Carrier
- 6%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. That is a cascade, and cascades start small and grow through the day. Across 1.27 million 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 80.2% on time here.
Cancellations run at 2.67%, against 2.23% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
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. 11.1% of arrivals land a full hour or more behind schedule, against 8.6% 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 1,199 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.
85,152 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.
What to do with this
Booking this route
Put together: avoid the 5pm–8pm departure. It runs 62.2% on time against 80.2% for the 5am–8am slot, and that 18 points is the largest single thing you control here. Delta Air Lines is the strongest operator if the fares are close.
Common questions
MIA to ORD questions
How often is MIA to ORD 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 29.3% of the 85,152 flights in this analysis, against 24.1% nationally. Delayed flights are late by roughly 55 minutes on average.
Which airline is most reliable on MIA to ORD?
Delta Air Lines leads at 81.6% on time across 13,705 flights. Frontier Airlines is at the other end on 68.6%, 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 MIA to ORD?
The 5am–8am departure window is the strongest at 80.2% on time. The 5pm–8pm window is the weakest at 62.2%, 18 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 January delays on MIA to ORD?
January is the weakest month at 63.7% on time, compared with 74.7% in May. Across the year that is 11 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
- Miami International (MIA) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- Delta Air Lines on-time record81.6%
- Frontier Airlines on-time record68.6%
- Why the first flight of the morning is statistically safest
- What a cancellation rate actually tells you (and what it hides)
The reverse direction, ORD to MIA, does not clear this site’s 365-flight floor and has no page of its own.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.