Route reliability record
IAD→LAS
Washington to Las Vegas
- Flights
- 1,069
- Period
- September 2025 to August 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 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 1,069 IAD to LAS flights, with a median arrival 13 minutes early.
Best time to fly IAD to LAS: a 11am–2pm departure, ideally on a Wednesday. Flights in that window arrived on time 88.4% of the time and Wednesday flights 90.5%, against 85.3% for the route overall.
Set against the rest of the country, this route's record is 8 points better than the US average of 77.3%. That gap is worth roughly 80 fewer late arrivals for every thousand flights.
Key figures
On time
85.3%
Arrivals under 15 minutes late, of 1,062 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
0.56%
National rate is 1.89%
Best carrier
United
88.0% on time across 965 flights
These figures cover 1,069 flights between September 2025 and August 2026. The median arrival is 13 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
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 | 965 | 88.0% | 80 min | 0.52% | A+ |
| Frontier Airlinesthin sample | 104 | 60.2% | 48 min | 0.96% | D+ |
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.
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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. 2 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. IAD → LASWashington to Las Vegas | United Airlines | 87.5% | 88.0% | 0.52% | 8am–11am, Wed | UA 1323 09:00 |
| 2. BWI → LASBaltimore to Las Vegas | Southwest Airlines | 77.5% | 78.3% | 0.99% | 5am–8am, Tue | — |
| 3. DCA → LASWashington to Las Vegas | Southwest Airlines | 48.6% | 49.4% | 1.64% | 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 is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 1,069 flights.
- 5am–8am—
- 8am–11am381 flights85.9%
- 11am–2pm364 flights88.4%
- 2pm–5pm—
- 5pm–8pm134 flights79.7%
- 8pm–5am190 flights82.1%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 11am–2pm slot at 88.4% on time, ahead of 5pm–8pm at 79.7%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 8am–11am window is the busiest, with 381 flights scheduled in it.
Explore
Filter IAD to LAS by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On IAD to LAS, the best departure window is 11am–2pm at 88.4% on time and the worst is 5pm–8pm at 79.7%, a real gap of 8.7 points. All US flights leaving 11am–2pm ran 78.3%.
- 5–8am—
- 8–11am85.9%
- 11am–2pm88.4%
- 2–5pm—
- 5–8pm79.7%
- 8pm–5am82.1%
best all US flightsScale 60% to 95%. Cells under 30 flights show a dash.
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.
June is the worst month at 71.1% 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. August was the busiest month here, with 111 flights.
Across the week, Wednesday is the strongest day at 90.5% on time and Sunday the weakest at 81.9%, a spread of 9 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 46% of the 11,000 delay minutes carriers reported here, and the remaining four split what is left.
- 46%Late-arriving aircraft
- 26%Carrier
- 20%National Airspace System
- 7%Extreme weather
46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 11,000 reported delay minutes here, that single category outweighs weather by 6 to one. The split is drawn from 11,104 reported delay minutes.
Cancellations are rare at 0.56%, 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 actually costs
5.6% 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 85.5% on time across 1,070 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. 1,069 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.
Work out the risk of missing a connection in LAS after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 1,069 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 85.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,062 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 14.7% of the 1,069 flights in this analysis, against 22.7% 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?
85.3% of flights arrive on time here against a national 77.3%, 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 11am–2pm departure window is the strongest at 88.4% on time. The 5pm–8pm window is the weakest at 79.7%, 9 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 June delays on IAD to LAS?
June is the weakest month at 71.1% 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
- United Airlines on IAD to LAS88.0%
- Frontier Airlines on IAD to LAS60.2%
- IAD to ATL, a related route78.0%
- LAX to LAS, a related route75.8%
- IAD to DEN, a related route83.1%
- United Airlines on-time record88.0%
- Frontier Airlines on-time record60.2%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.