Flight number record
UA 1535
United Airlines · Washington to Houston
- Route
- IAD → IAH
- Departs
- 12:50
- Flights
- 320
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1535, check with United Airlines.
UA 1535 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 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs an hour and a half. That rests on 320 flights, with a median arrival 12 minutes early.
Set against the rest of the country, UA 1535's record is 8 points better than the US average of 77.3%. That gap is worth roughly 78 fewer late arrivals for every thousand flights.
Key figures
On time
85.1%
Arrivals under 15 minutes late, of 316 completed flights
Avg delay
85 min
Across delayed arrivals only, not all flights
Cancelled
0.62%
National rate is 1.89%
1 hour+ late
5.7%
National rate is 8.3%
These figures cover 320 flights between September 2025 and August 2026. The median arrival is 12 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 1535 flies
UA 1535 flies IAD to IAH without a single fixed slot. Its most common scheduled departure was 12:50, used on 175 of 320 flights, with 12:55 (68 flights) next.
- Departs 12:50175 flights54.7%
- Departs 12:5568 flights21.3%
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 12:50 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and UA 1535 runs 7 points better at 85.1%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
UA 1535 next to IAD to IAH
Every carrier on IAD to IAH combined arrived on time 84.7% of the time across 1,862 flights, so UA 1535 is about level with it. Across its whole network United Airlines managed 78.8%, which this flight beats by 6 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1535thin sample | 320 | 85.1% | 85 min | 0.62% | A+ |
| All United Airlines on IAD–IAH | 1,862 | 84.7% | 71 min | 0.48% | B+ |
| All carriers on IAD–IAH | 1,862 | 84.7% | 71 min | 0.48% | B+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 1535 quarter by quarter
UA 1535 did not run the same all year. Its best quarter was Jan–Mar 2026 at 91.0% on time and its weakest Oct–Dec 2025 at 80.4%, a swing of 11 points on roughly 80 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 20256 flights—
- Oct–Dec 202592 flights80.4%
- Jan–Mar 202669 flights91.0%
- Apr–Jun 202691 flights86.5%
- Jul–Sep 202662 flights83.9%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
By weekday, UA 1535 did best on Sunday at 93.2% on time and worst on Friday at 76.1%. Each day rests on about 46 flights, so a gap of 17 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 1535 runs when it is late
UA 1535 often beats the schedule: 140 of 316 completed flights, 44%, arrived 15 minutes or more early. The 47 late arrivals split 15 under half an hour, 14 between 30 and 60 minutes, and 18 an hour or more.
- 15+ min early140 flights44.3%
- Within 15 min129 flights40.8%
- 15–29 min late15 flights4.7%
- 30–59 min late14 flights4.4%
- 1–2 hours late4 flights1.3%
- 2+ hours late14 flights4.4%
Scale runs 0% to 100%.
Share of 316 completed flights by arrival against schedule.
10 of 45 late departures made up the time and arrived on time, 22% of them. 12 flights left on time and still arrived late.
The worst days
Worst days for UA 1535
The latest arrival of the period was on 16 October 2025, 6 hours 49 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 16 October 2025 | 6 hours 49 minutes | Late-arriving aircraft |
| 16 March 2026 | 6 hours 6 minutes | Late-arriving aircraft |
| 18 July 2026 | 4 hours 51 minutes | Extreme weather |
| 1 October 2025 | 3 hours 24 minutes | Late-arriving aircraft |
| 6 August 2026 | 3 hours 13 minutes | Late-arriving aircraft |
Delay causes
Why UA 1535 runs late
Late-arriving aircraft accounts for 43% of the 3,999 delay minutes carriers reported here, and the remaining four split what is left.
- 43%Late-arriving aircraft
- 29%National Airspace System
- 22%Carrier
- 5%Extreme weather
43% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 3,999 reported delay minutes here, that single category outweighs weather by 8 to one. The split is drawn from 3,999 delay minutes reported on UA 1535.
Cancellations are rare at 0.62%, 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
5.7% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last an hour and a half, which a normal layover absorbs.
The 1,190 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 five other city pairs in the data, including IAH to DFW (217), RDU to IAD (180) and IAH to SFO (31), but none flew often enough under UA 1535 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to IAD to IAH only.
One caution: this is a thin sample. 320 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 1535
For a booking, UA 1535 has one of the better records a US domestic flight can show: 85.1% on time and 0.62% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- IAD to IAH, every carrier and departure
- IAH to IAD, the return direction
- United Airlines 2217 on the same route71.7%
- United Airlines 1524 on the same route89.8%
- Washington Dulles International (IAD) 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
- 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.