Route reliability record
IAD→LAX
Washington to Los Angeles
- Flights
- 2,460
- Period
- September 2025 to August 2026
- Distance
- 2,288 mi
- Carriers
- 2
This route earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 7 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 2,460 IAD to LAX flights, with a median arrival 9 minutes early.
Best time to fly IAD to LAX: a 11am–2pm departure, ideally on a Monday. Flights in that window arrived on time 90.1% of the time and Monday flights 86.9%, against 84.1% for the route overall.
Set against the rest of the country, this route's record is 7 points better than the US average of 77.3%. That gap is worth roughly 68 fewer late arrivals for every thousand flights.
Key figures
On time
84.1%
Arrivals under 15 minutes late, of 2,439 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
0.73%
National rate is 1.89%
Best carrier
United
84.6% on time across 2,340 flights
These figures cover 2,460 flights between September 2025 and August 2026. The median arrival is 9 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 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 | 2,340 | 84.6% | 61 min | 0.77% | B+ |
| American Airlinesthin sample | 120 | 75.0% | 53 min | 0.00% | B+ |
Flight by flight
Flights on IAD to LAX
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 Los Angeles
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. IAD → LAXWashington to Los Angeles | United Airlines | 83.9% | 84.6% | 0.77% | 5am–8am, Mon | UA 1689 12:35 |
| 2. BWI → LAXBaltimore to Los Angeles | United Airlines | 82.5% | 83.2% | 0.87% | 5am–8am, Tue | — |
| 3. DCA → LAXWashington to Los Angeles | American Airlines | 76.3% | 77.3% | 1.24% | 8am–11am, Mon | AA 1966 08:30 |
| 4. BWI → LAXBaltimore to Los Angeles | Southwest Airlines | 65.3% | 66.3% | 1.53% | 8am–11am, 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 14 points, against half a point between the best and worst carrier.
- 5am–8am353 flights86.4%
- 8am–11am414 flights88.5%
- 11am–2pm365 flights90.1%
- 2pm–5pm228 flights86.3%
- 5pm–8pm598 flights76.1%
- 8pm–5am502 flights83.2%
Scale runs 70% to 95%.
The best window here is not the first bank but the 11am–2pm slot at 90.1% on time, ahead of 5pm–8pm at 76.1%. 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 598 flights scheduled in it.
Explore
Filter IAD to LAX 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 LAX, the best departure window is 11am–2pm at 90.1% on time and the worst is 5pm–8pm at 76.1%, a wide gap of 14.0 points. All US flights leaving 11am–2pm ran 78.3%.
- 5–8am86.4%
- 8–11am88.5%
- 11am–2pm90.1%
- 2–5pm86.3%
- 5–8pm76.1%
- 8pm–5am83.2%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 13 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.
January is the weak month at 77.0% on time, against 90.2% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. June was the busiest month here, with 253 flights.
Across the week, Monday is the strongest day at 86.9% on time and Sunday the weakest at 82.1%, a spread of 5 points.
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 23,000 reported delay minutes.
- 33%Late-arriving aircraft
- 32%Carrier
- 26%National Airspace System
- 9%Extreme weather
No single cause dominates. late-arriving aircraft at 33%, carrier at 32% and national airspace system at 26% split the 23,000 reported delay minutes between them. An even spread like this usually means the operation is running close to its designed capacity with no one obvious weak point, and it is the hardest pattern for a traveller to route around. The split is drawn from 23,215 reported delay minutes.
Cancellations are rare at 0.73%, 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
Badly late arrivals are rare here: only 4.7% 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 return leg is a different operation and performs like one: it runs 87.5% on time across 2,461 flights, 3 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 3 points of difference.
The sample behind these figures is 2,460 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 LAX 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. September runs 90.2% on time and January 77.0%, a swing of 13 points. If the dates move at all, move them out of January before you think about anything else. 2,439 completed flights over 12 months sit behind that.
Common questions
IAD to LAX questions
How often is IAD to LAX delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 15.9% of the 2,460 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is IAD to LAX compared with the rest of the country?
84.1% of flights arrive on time here against a national 77.3%, a difference of 7 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 90.1% on time. The 5pm–8pm window is the weakest at 76.1%, 14 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 January delays on IAD to LAX?
January is the weakest month at 77.0% on time, compared with 90.2% in September. Across the year that is 13 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 IAD to LAX84.6%
- American Airlines on IAD to LAX75.0%
- IAD to ATL, a related route78.0%
- SFO to LAX, a related route70.9%
- IAD to DEN, a related route83.1%
- United Airlines on-time record84.6%
- American Airlines on-time record75.0%
- 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 LAX and LAX 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.