Carrier route record
UAORD→BUF
United Airlines · Chicago to Buffalo
- Flights
- 612
- Period
- July 2025 to June 2026
- Share of route
- 28%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on ORD to BUF 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 77.6%. The late ones land a little over an hour behind schedule. That rests on 612 flights. The strongest carrier on the route with a full sample, Envoy Air, flew 422 at 79.8% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on ORD to BUF from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
73.8%
Arrivals under 15 minutes late, of 604 completed flights
Avg delay
81 min
Across delayed arrivals only, not all flights
Cancelled
1.14%
National rate is 1.81%
Whole route
70.6%
Every carrier on ORD to BUF, 2,195 flights
These figures cover 612 flights between July 2025 and June 2026. Beyond the headline rate, 10.9% 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
United against every carrier on ORD to BUF
United flew 612 of the 2,195 flights on ORD to BUF, about 28% of it. Its 73.8% on time is 3 points better than the route as a whole, which runs 70.6%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from Envoy at 79.8% to American at 58.8%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
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 (this page) | 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
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 33 points, against 21 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am129 flights93.8%
- 8am–11am1 flights—
- 11am–2pm—
- 2pm–5pm175 flights81.1%
- 5pm–8pm307 flights61.0%
- 8pm–5am—
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 61.0% on time, against 93.8% 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 5pm–8pm window is the busiest, with 307 flights scheduled in it.
Across the year
United on ORD to BUF through the year
January is the weak month at 58.1% on time, against 83.1% in September. 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. September was the busiest month here, with 89 flights.
Across the week, Tuesday is the strongest day at 81.3% on time and Sunday the weakest at 66.2%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 44% of the 13,000 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.
- 44%Late-arriving aircraft
- 33%Carrier
- 14%National Airspace System
- 8%Extreme weather
44% 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 13,000 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 12,866 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 93.8% on time here.
Cancellations sit at 1.14% against a national 1.81%, which is ordinary. Diversions add another 0.16%.
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. 10.9% 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 runs 74.1% on time across 612 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 612 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 United on ORD to BUF
Put together: treat all of this as provisional. 612 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 73.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 604 completed flights over 12 months sit behind that.
Related
Where to go next
- ORD to BUF, every carrier
- United on BUF to ORD, the return leg
- Envoy Air on ORD to BUF79.8%
- Republic Airways on ORD to BUF74.3%
- SkyWest Airlines on ORD to BUF66.1%
- American Airlines on ORD to BUF58.8%
- United Airlines network-wide record
- Chicago O'Hare International (ORD) delay statistics
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
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.