Flight number record
UA 2638
United Airlines · Chicago to Houston
- Route
- ORD → IAH
- Departs
- 10:35
- Flights
- 259
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 2638, check with United Airlines.
UA 2638 earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs about 55 minutes. That rests on 259 flights, with a median arrival 14 minutes early.
Set against the rest of the country, UA 2638's record is 9 points better than the US average of 77.3%. That gap is worth roughly 87 fewer late arrivals for every thousand flights.
Key figures
On time
86.0%
Arrivals under 15 minutes late, of 258 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
1 hour+ late
3.5%
National rate is 8.3%
These figures cover 259 flights between September 2025 and August 2026. The median arrival is 14 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
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Schedule
When UA 2638 flies
UA 2638 flies ORD to IAH without a single fixed slot. Its most common scheduled departure was 10:35, used on 133 of 259 flights, with 08:50 (37 flights) and 10:25 (35 flights) next.
- Departs 10:35133 flights51.4%
- Departs 08:5037 flights14.3%
- Departs 10:2535 flights13.5%
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 10:35 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and UA 2638 runs 2 points better at 86.0%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
UA 2638 next to ORD to IAH
Every carrier on ORD to IAH combined arrived on time 76.0% of the time across 6,141 flights, so UA 2638 is 10 points ahead of it. United flew 4,080 flights on the same city pair under all its flight numbers, including this one, and those ran 80.0% on time. Across its whole network United Airlines managed 78.8%, which this flight beats by 7 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 2638thin sample | 259 | 86.0% | 55 min | 0.00% | A+ |
| All United Airlines on ORD–IAH | 4,080 | 80.0% | 70 min | 0.66% | B+ |
| All carriers on ORD–IAH | 6,141 | 76.0% | 74 min | 1.40% | B |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 2638 quarter by quarter
UA 2638 did not run the same all year. Its best quarter was Oct–Dec 2025 at 94.1% on time and its weakest Apr–Jun 2026 at 80.4%, a swing of 14 points on roughly 65 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.
- Oct–Dec 202551 flights94.1%
- Jan–Mar 202690 flights83.1%
- Apr–Jun 202656 flights80.4%
- Jul–Sep 202662 flights88.7%
Scale runs 70% to 100%.
By weekday, UA 2638 did best on Thursday at 94.6% on time and worst on Friday at 75.7%. Each day rests on about 37 flights, so a gap of 19 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 2638 runs when it is late
UA 2638 often beats the schedule: 126 of 258 completed flights, 49%, arrived 15 minutes or more early. The 36 late arrivals split 15 under half an hour, 12 between 30 and 60 minutes, and 9 an hour or more.
- 15+ min early126 flights48.8%
- Within 15 min96 flights37.2%
- 15–29 min late15 flights5.8%
- 30–59 min late12 flights4.7%
- 1–2 hours late5 flights1.9%
- 2+ hours late4 flights1.6%
Scale runs 0% to 100%.
Share of 258 completed flights by arrival against schedule.
A late pushback is often recovered here: of 40 departures that left 15 minutes late or more, 16 still arrived on time. 12 flights left on time and still arrived late.
The worst days
Worst days for UA 2638
The latest arrival of the period was on 16 March 2026, 4 hours 8 minutes behind schedule; most of its delay minutes were filed as national airspace system delay. The five worst days are spread across March, December, April, January and August, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 16 March 2026 | 4 hours 8 minutes | National Airspace System |
| 29 December 2025 | 2 hours 35 minutes | Late-arriving aircraft |
| 14 April 2026 | 2 hours 14 minutes | Carrier |
| 25 January 2026 | 2 hours 5 minutes | Extreme weather |
| 12 August 2026 | 1 hour 47 minutes | National Airspace System |
Delay causes
Why UA 2638 runs late
National Airspace System accounts for 51% of the 1,961 delay minutes carriers reported here, and the remaining four split what is left.
- 51%National Airspace System
- 24%Carrier
- 20%Late-arriving aircraft
- 6%Extreme weather
51% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 991 minutes out of 1,961, against a national NAS share of 21%. The split is drawn from 1,961 delay minutes reported on UA 2638.
Cancellations are rare at 0.00%, below the national 1.89% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 3.5% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 925 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 seven other city pairs in the data, including RDU to ORD (135), IAH to SEA (123) and IAH to SAN (55), but none flew often enough under UA 2638 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ORD to IAH only.
One caution: this is a thin sample. 259 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 2638
For a booking, UA 2638 has one of the better records a US domestic flight can show: 86.0% on time and 0.00% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- ORD to IAH, every carrier and departure
- IAH to ORD, the return direction
- Frontier Airlines 3135 on the same route78.6%
- American Airlines 3144 on the same route52.5%
- United Airlines 1231 on the same route91.4%
- United Airlines 2426 on the same route72.3%
- Chicago O'Hare International (ORD) delay statistics
- George Bush Intercontinental (IAH) 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
- Worst months to fly in the US, ranked by the data
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.