Route reliability record
ORD→BUF
Chicago to Buffalo
- Flights
- 2,195
- Period
- July 2025 to June 2026
- Distance
- 474 mi
- Carriers
- 5
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, 7 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 2,195 flights, of which Envoy Air flew 422 at 79.8% on time.
Envoy Air is the most reliable of the three carriers covered here at 79.8% on time across 422 flights.
Key figures
On time
70.6%
Arrivals under 15 minutes late, of 2,131 completed flights
Avg delay
80 min
Across delayed arrivals only, not all flights
Cancelled
2.64%
National rate is 1.81%
Best carrier
Envoy
79.8% on time across 422 flights
These figures cover 2,195 flights between July 2025 and June 2026. Beyond the headline rate, 12.0% 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 BUF
The choice of carrier is not cosmetic here. Envoy Air arrives on time 79.8% of the time; American Airlines manages 58.8%. Sample sizes sit next to every figure, because a two-point gap across 476 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Air | 422 | 79.8% | 60 min | 2.61% | B |
| Republic Airwaysthin sample | 355 | 74.3% | 74 min | 5.07% | C− |
| United Airlines | 612 | 73.8% | 81 min | 1.14% | C |
| SkyWest Airlinesthin sample | 330 | 66.1% | 84 min | 4.85% | C− |
| American Airlines | 476 | 58.8% | 88 min | 1.26% | D |
The spread between Envoy and American is 21 points, wide enough that it should decide the booking. On a hundred trips that is 21 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 38 points, against 21 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am317 flights87.5%
- 8am–11am327 flights78.2%
- 11am–2pm219 flights75.5%
- 2pm–5pm552 flights75.8%
- 5pm–8pm551 flights58.0%
- 8pm–5am229 flights49.5%
Scale runs 40% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 49.5% 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 2pm–5pm window is the busiest, with 552 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 16 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.
July is the worst month at 61.7% on time, 16 points below September, the best at 78.1%. 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 217 flights.
Across the week, Tuesday is the strongest day at 75.2% on time and Sunday the weakest at 62.8%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 48% of the 50,000 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.
- 48%Late-arriving aircraft
- 28%Carrier
- 16%National Airspace System
- 8%Extreme weather
48% 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 50,000 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 split is drawn from 49,945 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 run at 2.64%, against 1.81% 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. 12.0% 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.
At 474 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 74.0% on time across 2,196 flights, 3 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 3 points of difference.
The sample behind these figures is 2,195 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 78.1% on time and July 61.7%, a swing of 16 points. If the dates move at all, move them out of July before you think about anything else. 2,131 completed flights over 12 months sit behind that.
Common questions
ORD to BUF questions
How often is ORD to BUF 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 29.4% of the 2,195 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 ORD to BUF?
Envoy Air leads at 79.8% on time across 422 flights. American Airlines is at the other end on 58.8%, a gap of 21 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 BUF?
The 5am–8am departure window is the strongest at 87.5% on time. The 8pm–5am window is the weakest at 49.5%, 38 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 ORD to BUF?
July is the weakest month at 61.7% on time, compared with 78.1% in September. Across the year that is 16 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
- BUF to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Envoy Air on-time record79.8%
- Republic Airways on-time record74.3%
- United Airlines on-time record73.8%
- Why the first flight of the morning is statistically safest
- What a cancellation rate actually tells you (and what it hides)
Direction matters. ORD to BUF and BUF 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, July 2025 to June 2026. Updated monthly. How this data is collected.