Carrier route record
UAIAD→LAS
United Airlines · Washington to Las Vegas
- Flights
- 965
- Period
- September 2025 to August 2026
- Share of route
- 90%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on IAD to LAS 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 a little over an hour. That rests on 965 flights, with a median arrival 14 minutes early.
Set against the rest of the country, United's IAD to LAS record is 11 points better than the US average of 77.3%. That gap is worth roughly 107 fewer late arrivals for every thousand flights.
Key figures
On time
88.0%
Arrivals under 15 minutes late, of 959 completed flights
Avg delay
80 min
Across delayed arrivals only, not all flights
Cancelled
0.52%
National rate is 1.89%
Whole route
85.3%
Every carrier on IAD to LAS, 1,069 flights
These figures cover 965 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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Carrier by carrier
United against every carrier on IAD to LAS
United flew 965 of the 1,069 flights on IAD to LAS, most of the route. Its 88.0% on time is 3 points better than the route as a whole, which runs 85.3%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 88.0% to Frontier at 60.2%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 965 | 88.0% | 80 min | 0.52% | A+ |
| Frontier Airlinesthin sample | 104 | 60.2% | 48 min | 0.96% | D+ |
Flight by flight
United flight numbers on IAD to LAS
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 16 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am277 flights95.6%
- 11am–2pm364 flights88.4%
- 2pm–5pm—
- 5pm–8pm134 flights79.7%
- 8pm–5am190 flights82.1%
Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 95.6% of the time, against 79.7% for the evening window. That is 16 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 364 flights scheduled in it.
Across the year
United on IAD to LAS through the year
June is the worst month at 78.3% on time, 17 points below April, the best at 95.1%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. October was the busiest month here, with 93 flights.
Across the week, Wednesday is the strongest day at 93.2% on time and Sunday the weakest at 84.3%, a spread of 9 points.
Arrival by arrival
How late United on IAD to LAS runs when it is late
United on IAD to LAS often beats the schedule: 474 of 959 completed flights, 49%, arrived 15 minutes or more early. The 115 late arrivals split 34 under half an hour, 30 between 30 and 60 minutes, and 51 an hour or more.
- 15+ min early474 flights49.4%
- Within 15 min370 flights38.6%
- 15–29 min late34 flights3.5%
- 30–59 min late30 flights3.1%
- 1–2 hours late25 flights2.6%
- 2+ hours late26 flights2.7%
Scale runs 0% to 100%.
Share of 959 completed flights by arrival against schedule.
36 of 121 late departures made up the time and arrived on time, 30% of them. 30 flights left on time and still arrived late.
The worst days
Worst days for United on IAD to LAS
The latest arrival of the period was on 16 August 2026, 5 hours 13 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On three of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 16 August 2026 | 5 hours 13 minutes | Carrier |
| 29 June 2026 | 4 hours 52 minutes | Late-arriving aircraft |
| 7 August 2026 | 4 hours 47 minutes | Late-arriving aircraft |
| 16 October 2025 | 4 hours 46 minutes | Late-arriving aircraft |
| 9 July 2026 | 4 hours 38 minutes | Carrier |
Delay causes
Why United runs late on this route
Late-arriving aircraft accounts for 45% of the 9,138 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Late-arriving aircraft
- 25%Carrier
- 21%National Airspace System
- 9%Extreme weather
45% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 9,138 reported delay minutes here, that single category outweighs weather by 5 to one. The split is drawn from 9,138 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 95.6% on time here.
Cancellations are rare at 0.52%, 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 stage length
What a delay here costs
5.3% 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 a little over an hour, which a normal layover absorbs.
At 2,065 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 return leg runs 88.2% on time across 967 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 965 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 United on IAD to LAS
Put together: treat all of this as provisional. 965 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 88.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 959 completed flights over 12 months sit behind that.
Related
Where to go next
- IAD to LAS, every carrier
- United on LAS to IAD, the return leg
- Frontier Airlines on IAD to LAS60.2%
- United Airlines network-wide record
- Washington Dulles International (IAD) delay statistics
- Harry Reid International (LAS) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.