Route reliability record
IAD→LAX
Washington to Los Angeles
- Flights
- 2,454
- Period
- July 2025 to June 2026
- Distance
- 2,288 mi
- Carriers
- 3
This route lands a B+, 4 points better than the national rate of 77.6%. Roughly one flight in five arrive 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 2,454 flights, with a median arrival 8 minutes early.
Set against the rest of the country, this route's record is 4 points better than the US average of 77.6%. That gap is worth roughly 42 fewer late arrivals for every thousand flights.
Key figures
On time
81.8%
Arrivals under 15 minutes late, of 2,428 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
0.94%
National rate is 1.81%
Best carrier
United
83.1% on time across 2,320 flights
These figures cover 2,454 flights between July 2025 and June 2026. The median arrival is 8 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 LAX
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 | 2,320 | 83.1% | 63 min | 0.99% | B+ |
| American Airlinesthin sample | 84 | 72.6% | 37 min | 0.00% | C+ |
| Alaska Airlinesthin sample | 50 | 34.0% | 75 min | 0.00% | F+ |
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 17 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–8am302 flights86.4%
- 8am–11am382 flights87.9%
- 11am–2pm365 flights90.6%
- 2pm–5pm234 flights82.8%
- 5pm–8pm599 flights73.3%
- 8pm–5am572 flights77.9%
Scale runs 65% 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 90.6% on time, ahead of 5pm–8pm at 73.3%. 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 5pm–8pm window is the busiest, with 599 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 30 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 60.0% on time, 30 points below September, the best at 90.2%. 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. June was the busiest month here, with 253 flights.
The day of the week is close to irrelevant here: 4 points separates the best day from the worst. Weekly demand peaks are not what drives the delays on this operation.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 28,000 reported delay minutes.
- 36%Carrier
- 35%Late-arriving aircraft
- 21%National Airspace System
- 8%Extreme weather
- 0%Security
35% 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 28,000 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. The split is drawn from 27,671 reported delay minutes.
The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 9,906 of the 28,000 delay minutes reported here.
Cancellations sit at 0.94% against a national 1.81%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here actually costs
5.5% 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 are the about an hour kind, which a normal layover absorbs.
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 return leg is a different operation and performs like one: it runs 86.7% on time across 2,454 flights, 5 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.
The sample behind these figures is 2,454 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.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 90.2% on time and July 60.0%, a swing of 30 points. If the dates move at all, move them out of July before you think about anything else. 2,428 completed flights over 12 months sit behind that.
Common questions
IAD to LAX questions
How often is IAD to LAX delayed?
Roughly one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.2% of the 2,454 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is IAD to LAX compared with the rest of the country?
81.8% of flights arrive on time here against a national 77.6%, a difference of 4 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on IAD to LAX?
The 11am–2pm departure window is the strongest at 90.6% on time. The 5pm–8pm window is the weakest at 73.3%, 17 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 LAX?
July is the weakest month at 60.0% on time, compared with 90.2% in September. Across the year that is 30 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
- LAX to IAD — the return legseparate record
- Washington Dulles International (IAD) delay statistics
- Los Angeles International (LAX) delay statistics
- United Airlines on-time record83.1%
- American Airlines on-time record72.6%
- Alaska Airlines on-time record34.0%
- 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 LAX and LAX to IAD are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.