Flight number record
UA 636
United Airlines · Chicago to Burlington
- Route
- ORD → BTV
- Departs
- 18:20
- Flights
- 297
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 2026, not live status. For today’s UA 636, check with United Airlines.
UA 636 draws a D+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 297 flights, with a median arrival 5 minutes late.
The national on-time rate over the same period is 77.6%, so UA 636 runs 13 points behind the country as a whole. Across a thousand flights that is about 133 extra late arrivals.
Key figures
On time
64.3%
Arrivals under 15 minutes late, of 294 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.67%
National rate is 1.81%
1 hour+ late
10.9%
National rate is 8.1%
These figures cover 297 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.
Schedule
When UA 636 flies
UA 636 flies ORD to BTV without a single fixed slot. Its most common scheduled departure was 18:20, used on 74 of 297 flights, with 18:10 (44 flights) and 18:09 (37 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 18:2074 flights24.9%
- Departs 18:1044 flights14.8%
- Departs 18:0937 flights12.5%
Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 18:20 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and UA 636 runs 4 points worse at 64.3%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
Against the route
UA 636 next to ORD to BTV
Every carrier on ORD to BTV combined arrived on time 69.0% of the time across 1,245 flights, so UA 636 is 5 points behind it. United flew 683 flights on the same city pair under all its flight numbers, including this one, and those ran 72.6% on time. Across its whole network United Airlines managed 79.0%, which this flight trails by 15 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 636thin sample | 297 | 64.3% | 61 min | 0.67% | D+ |
| All United Airlines on ORD–BTV | 683 | 72.6% | 62 min | 0.73% | C+ |
| All carriers on ORD–BTV | 1,245 | 69.0% | 75 min | 1.93% | C |
| United Airlines, whole network | 821,041 | 79.0% | 72 min | 1.01% | B |
Across the year
UA 636 quarter by quarter
UA 636 did not run the same all year. Its best quarter was Jul–Sep 2025 at 79.1% on time and its weakest Jan–Mar 2026 at 55.7%, a swing of 23 points on roughly 74 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202543 flights79.1%
- Oct–Dec 202575 flights71.6%
- Jan–Mar 202690 flights55.7%
- Apr–Jun 202689 flights59.6%
Scale runs 45% to 85%. Rows with fewer than 30 flights show a dash.
By weekday, UA 636 did best on Friday at 73.8% on time and worst on Thursday at 50.0%. Each day rests on about 42 flights, so a gap of 24 points is worth noticing but could still narrow in another year.
Delay causes
Why UA 636 runs late
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 6,360 reported delay minutes.
- 39%Late-arriving aircraft
- 28%Carrier
- 23%National Airspace System
- 10%Extreme weather
39% 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 6,360 reported delay minutes here, that single category outweighs weather by 4 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 6,360 delay minutes reported on UA 636.
Cancellations are rare at 0.67%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight 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.
The 763 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 same number turns up on nine other city pairs in the data, including HDN to ORD (90), PNS to ORD (66) and PHX to IAH (49), but none flew often enough under UA 636 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ORD to BTV only.
One caution: this is a thin sample. 297 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 UA 636
For a booking, read UA 636 as 64.3% on time with 0.67% cancelled over 297 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- ORD to BTV, every carrier and departure
- BTV to ORD, the return direction
- United Airlines 786 on the same route82.3%
- Chicago O'Hare International (ORD) delay statistics
- United Airlines on-time record
- Every United Airlines flight number with a record
- The most and least reliable flight numbers in the US
- Why the first flight of the morning is statistically safest
A flight number here means United Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
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.