Route reliability record
IAD→LAS
Washington to Las Vegas
- Flights
- 1,108
- Period
- July 2025 to June 2026
- Distance
- 2,065 mi
- Carriers
- 2
This route 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 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 1,108 IAD to LAS flights, with a median arrival 12 minutes early.
Best time to fly IAD to LAS: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 89.5% of the time and Wednesday flights 87.4%, against 85.1% for the route overall.
Set against the rest of the country, this route's record is 8 points better than the US average of 77.6%. That gap is worth roughly 75 fewer late arrivals for every thousand flights.
Key figures
On time
85.1%
Arrivals under 15 minutes late, of 1,102 completed flights
Avg delay
69 min
Across delayed arrivals only, not all flights
Cancelled
0.45%
National rate is 1.81%
Best carrier
United
86.8% on time across 1,009 flights
These figures cover 1,108 flights between July 2025 and June 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.
Carrier by carrier
Which airline is most reliable on IAD to LAS
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 | 1,009 | 86.8% | 70 min | 0.50% | A+ |
| Frontier Airlinesthin sample | 99 | 67.7% | 67 min | 0.00% | C+ |
Flight by flight
Flights on IAD to LAS
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
Best ways to make this trip
The most reliable ways to fly Washington to Las Vegas
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. DCA → LASWashington to Las Vegas | American Airlines | 88.2% | 89.4% | 1.37% | 5am–8am, Sun | — |
| 2. IAD → LASWashington to Las Vegas | United Airlines | 86.4% | 86.8% | 0.50% | 8am–11am, Wed (route) | UA 1323 09:00 |
| 3. BWI → LASBaltimore to Las Vegas | Southwest Airlines | 77.2% | 78.1% | 1.10% | 5am–8am, Tue | — |
| 4. DCA → LASWashington to Las Vegas | Southwest Airlines | 52.8% | 53.4% | 1.10% | 5am–8am, Sat | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
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. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am50 flights74.0%
- 8am–11am366 flights89.5%
- 11am–2pm316 flights87.9%
- 2pm–5pm—
- 5pm–8pm165 flights74.4%
- 8pm–5am211 flights84.4%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 89.5% of the time, against 74.0% for the early 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 8am–11am window is the busiest, with 366 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 24 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 70.7% on time, 24 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. July was the busiest month here, with 123 flights.
Across the week, Wednesday is the strongest day at 87.4% on time and Monday the weakest at 82.1%. 5 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 11,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 46%Late-arriving aircraft
- 23%Carrier
- 18%National Airspace System
- 12%Extreme weather
Extreme weather accounts for 12% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.0 times the usual weather exposure. The split is drawn from 11,330 reported delay minutes.
46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 11,000 reported delay minutes here, that single category outweighs weather by 4 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit.
Cancellations are rare at 0.45%, below the national 1.81% 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 actually costs
5.3% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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 87.1% on time across 1,109 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,108 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in LAS after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 95.1% on time and July 70.7%, a swing of 24 points. If the dates move at all, move them out of July before you think about anything else. 1,102 completed flights over 12 months sit behind that.
Common questions
IAD to LAS questions
How often is IAD to LAS delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 14.9% of the 1,108 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is IAD to LAS compared with the rest of the country?
85.1% of flights arrive on time here against a national 77.6%, a difference of 8 points in its favour. That is worth a A+ on this site's grading scale.
What time of day has the fewest delays on IAD to LAS?
The 8am–11am departure window is the strongest at 89.5% on time. The 5am–8am window is the weakest at 74.0%, 16 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on IAD to LAS?
July is the weakest month at 70.7% on time, compared with 95.1% in April. Across the year that is 24 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- LAS to IAD — the return legseparate record
- Washington Dulles International (IAD) delay statistics
- Harry Reid International (LAS) delay statistics
- IAD to ATL, a related route79.2%
- LAX to LAS, a related route76.5%
- IAD to DEN, a related route81.7%
- United Airlines on-time record86.8%
- Frontier Airlines on-time record67.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. IAD to LAS and LAS to IAD are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.