Flight number record
UA 1635
United Airlines · Los Angeles to Washington
- Route
- LAX → IAD
- Departs
- 12:43
- Flights
- 347
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1635, check with United Airlines.
UA 1635 earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 11 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 347 flights, with a median arrival 11 minutes early.
Set against the rest of the country, UA 1635's record is 11 points better than the US average of 77.3%. That gap is worth roughly 113 fewer late arrivals for every thousand flights.
Key figures
On time
88.6%
Arrivals under 15 minutes late, of 342 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
0.58%
National rate is 1.89%
1 hour+ late
3.5%
National rate is 8.3%
These figures cover 347 flights between September 2025 and August 2026. The median arrival is 11 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 1635 flies
UA 1635 flies LAX to IAD without a single fixed slot. Its most common scheduled departure was 12:43, used on 82 of 347 flights, with 12:55 (63 flights) and 12:45 (51 flights) next.
- Departs 12:4382 flights23.6%
- Departs 12:5563 flights18.2%
- Departs 12:4551 flights14.7%
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 12:43 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and UA 1635 runs 10 points better at 88.6%. 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 1635 next to LAX to IAD
Every carrier on LAX to IAD combined arrived on time 87.5% of the time across 2,461 flights, so UA 1635 is about level with it. United flew 2,341 flights on the same city pair under all its flight numbers, including this one, and those ran 88.0% on time. Across its whole network United Airlines managed 78.8%, which this flight beats by 10 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1635thin sample | 347 | 88.6% | 65 min | 0.58% | A+ |
| All United Airlines on LAX–IAD | 2,341 | 88.0% | 54 min | 0.56% | A+ |
| All carriers on LAX–IAD | 2,461 | 87.5% | 56 min | 0.53% | A+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 1635 quarter by quarter
UA 1635 did not run the same all year. Its best quarter was Oct–Dec 2025 at 93.5% on time and its weakest Jul–Sep 2026 at 77.4%, a swing of 16 points on roughly 87 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 flights—
- Oct–Dec 202592 flights93.5%
- Jan–Mar 202672 flights91.4%
- Apr–Jun 202691 flights92.2%
- Jul–Sep 202662 flights77.4%
Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, UA 1635 ranged from 84.4% on Tuesday to 93.3% on Wednesday. With about 50 flights behind each day, a spread of 9 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late UA 1635 runs when it is late
UA 1635 often beats the schedule: 132 of 342 completed flights, 39%, arrived 15 minutes or more early. The 39 late arrivals split 13 under half an hour, 14 between 30 and 60 minutes, and 12 an hour or more.
- 15+ min early132 flights38.6%
- Within 15 min171 flights50.0%
- 15–29 min late13 flights3.8%
- 30–59 min late14 flights4.1%
- 1–2 hours late4 flights1.2%
- 2+ hours late8 flights2.3%
Scale runs 0% to 100%.
Share of 342 completed flights by arrival against schedule.
A late pushback is often recovered here: of 39 departures that left 15 minutes late or more, 14 still arrived on time. 14 flights left on time and still arrived late.
The worst days
Worst days for UA 1635
The latest arrival of the period was on 25 September 2025, 4 hours 50 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across September, June, January, July and March, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 25 September 2025 | 4 hours 50 minutes | Late-arriving aircraft |
| 19 June 2026 | 3 hours 39 minutes | Carrier |
| 5 January 2026 | 2 hours 41 minutes | Carrier |
| 18 July 2026 | 2 hours 32 minutes | National Airspace System |
| 15 March 2026 | 2 hours 23 minutes | National Airspace System |
Delay causes
Why UA 1635 runs late
Carrier accounts for 44% of the 2,525 delay minutes carriers reported here, and the remaining four split what is left.
- 44%Carrier
- 30%National Airspace System
- 26%Late-arriving aircraft
The largest share of delay minutes, 44%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,115 of the 2,525 delay minutes reported here. The split is drawn from 2,525 delay minutes reported on UA 1635.
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
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.
At 2,288 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The same number turns up on two other city pairs in the data, including IAD to ATL (121) and SEA to LAX (25), but none flew often enough under UA 1635 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to LAX to IAD only.
One caution: this is a thin sample. 347 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 1635
For a booking, UA 1635 has one of the better records a US domestic flight can show: 88.6% on time and 0.58% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- LAX to IAD, every carrier and departure
- IAD to LAX, the return direction
- United Airlines 2667 on the same route90.6%
- United Airlines 2282 on the same route88.8%
- Los Angeles International (LAX) delay statistics
- Washington Dulles International (IAD) 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.