Flight number record
UA 636
United Airlines · Chicago to Burlington
- Route
- ORD → BTV
- Departs
- 18:15
- Flights
- 345
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 636, check with United Airlines.
UA 636 draws a D+. Roughly one flight in two 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 345 flights, with a median arrival 9 minutes late.
The national on-time rate over the same period is 77.3%, so UA 636 runs 18 points behind the country as a whole. Across a thousand flights that is about 176 extra late arrivals.
Key figures
On time
59.7%
Arrivals under 15 minutes late, of 340 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
0.58%
National rate is 1.89%
1 hour+ late
12.9%
National rate is 8.3%
These figures cover 345 flights between September 2025 and August 2026. Beyond the headline rate, 12.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When UA 636 flies
UA 636 flies ORD to BTV without a single fixed slot. Its most common scheduled departure was 18:15, used on 90 of 345 flights, with 18:20 (61 flights) and 18:10 (50 flights) next.
- Departs 18:1590 flights26.1%
- Departs 18:2061 flights17.7%
- Departs 18:1050 flights14.5%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 18:15 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and UA 636 runs 8 points worse at 59.7%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
UA 636 next to ORD to BTV
Every carrier on ORD to BTV combined arrived on time 68.5% of the time across 1,282 flights, so UA 636 is 9 points behind it. United flew 684 flights on the same city pair under all its flight numbers, including this one, and those ran 70.1% on time. Across its whole network United Airlines managed 78.8%, which this flight trails by 19 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 636thin sample | 345 | 59.7% | 64 min | 0.58% | D+ |
| All United Airlines on ORD–BTV | 684 | 70.1% | 65 min | 0.44% | C+ |
| All carriers on ORD–BTV | 1,282 | 68.5% | 74 min | 2.03% | C |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | 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 73.3% on time and its weakest Jul–Sep 2026 at 44.1%, a swing of 29 points on roughly 69 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 202530 flights73.3%
- Oct–Dec 202575 flights71.6%
- Jan–Mar 202690 flights55.7%
- Apr–Jun 202689 flights59.6%
- Jul–Sep 202661 flights44.1%
Scale runs 35% to 80%.
By weekday, UA 636 did best on Friday at 69.4% on time and worst on Monday at 52.0%. Each day rests on about 49 flights, so a gap of 17 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 636 runs when it is late
The 137 late arrivals split 53 under half an hour, 40 between 30 and 60 minutes, and 44 an hour or more.
- 15+ min early45 flights13.2%
- Within 15 min158 flights46.5%
- 15–29 min late53 flights15.6%
- 30–59 min late40 flights11.8%
- 1–2 hours late24 flights7.1%
- 2+ hours late20 flights5.9%
Scale runs 0% to 100%.
Share of 340 completed flights by arrival against schedule.
16 of 105 late departures made up the time and arrived on time, 15% of them. In the other direction, 48 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at BTV.
The worst days
Worst days for UA 636
The latest arrival of the period was on 28 July 2026, 6 hours 39 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across July, June, November and August, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 28 July 2026 | 6 hours 39 minutes | Carrier |
| 24 June 2026 | 5 hours 10 minutes | Extreme weather |
| 30 November 2025 | 4 hours | Carrier |
| 10 June 2026 | 3 hours 39 minutes | Late-arriving aircraft |
| 9 August 2026 | 3 hours 36 minutes | Late-arriving aircraft |
Delay causes
Why UA 636 runs late
Late-arriving aircraft accounts for 44% of the 8,732 delay minutes carriers reported here, and the remaining four split what is left.
- 44%Late-arriving aircraft
- 26%Carrier
- 23%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. Across 8,732 reported delay minutes here, that single category outweighs weather by 6 to one. The split is drawn from 8,732 delay minutes reported on UA 636.
Cancellations are rare at 0.58%, below the national 1.89% 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
12.9% 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 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.
The same number turns up on six other city pairs in the data, including HDN to ORD (90), MSO to ORD (82) and PNS to ORD (66), 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. 345 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, UA 636 is a flight to put a long connection behind. 12.9% of its completed flights arrived an hour or more late, which a short layover will not absorb. If the onward flight is on a separate ticket, the risk sits with you.
Related
Where to go next
- ORD to BTV, every carrier and departure
- BTV to ORD, the return direction
- United Airlines 786 on the same route80.8%
- 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.