Route reliability record
SEA→LAX
Seattle to Los Angeles
- Flights
- 7,410
- Period
- June 2025 to May 2026
- Distance
- 954 mi
- Carriers
- 6
This route lands a B+, 6 points better than the national rate of 77.4%. About one flight in six 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 7,410 flights, of which United Airlines flew 393 at 90.3% on time.
United Airlines is the most reliable of the four carriers covered here at 90.3% on time across 393 flights.
Key figures
On time
83.0%
Arrivals under 15 minutes late, of 7,338 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
0.93%
National rate is 1.80%
Best carrier
United
90.3% on time across 393 flights
These figures cover 7,410 flights between June 2025 and May 2026. The median arrival is 7 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 SEA to LAX
The choice of carrier is not cosmetic here. United Airlines arrives on time 90.3% of the time; Alaska Airlines manages 79.9%. Sample sizes sit next to every figure, because a two-point gap across 3,285 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| United Airlines | 393 | 90.3% | 94 min | 0.25% | A+ |
| SkyWest Airlines | 1,248 | 85.6% | 108 min | 0.64% | A+ |
| Delta Air Lines | 2,222 | 85.0% | 60 min | 0.63% | A+ |
| Alaska Airlines | 3,285 | 79.9% | 44 min | 1.10% | B |
| Frontier Airlinesthin sample | 261 | 79.7% | 59 min | 3.83% | B− |
United leads Alaska by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 13 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,392 flights88.6%
- 8am–11am1,261 flights86.9%
- 11am–2pm1,107 flights83.6%
- 2pm–5pm1,043 flights82.0%
- 5pm–8pm1,646 flights79.4%
- 8pm–5am961 flights76.1%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 88.6% of the time, against 76.1% for the overnight window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
Across the year
When delays peak on this route
This route's year swings by 16 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.
December is the weak month at 73.8% on time, against 89.5% in April. 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.
Across the week, Tuesday is the strongest day at 85.8% on time and Sunday the weakest at 80.2%. 6 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. Carrier accounts for 53% of the 74,000 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.
- 53%Carrier
- 31%Late-arriving aircraft
- 14%National Airspace System
- 3%Extreme weather
- 0%Security
The largest share of delay minutes, 53%, 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 39,000 of the 74,000 delay minutes reported here.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 88.6% on time here.
Cancellations sit at 0.93% against a national 1.80%, which is ordinary. Diversions add another 0.04%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.5% land an hour or more behind schedule, against 8.2% 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.
The 954 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 85.2% on time across 7,405 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 7,410 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. April runs 89.5% on time and December 73.8%, a swing of 16 points. If the dates move at all, move them out of December before you think about anything else.
Common questions
SEA to LAX questions
How often is SEA to LAX delayed?
About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.0% of the 7,410 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SEA to LAX?
United Airlines leads at 90.3% on time across 393 flights. Alaska Airlines is at the other end on 79.9%, a gap of 10 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on SEA to LAX?
The 5am–8am departure window is the strongest at 88.6% on time. The 8pm–5am window is the weakest at 76.1%, 13 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 December delays on SEA to LAX?
December is the weakest month at 73.8% on time, compared with 89.5% in April. Across the year that is 16 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 SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Los Angeles International (LAX) delay statistics
- American Airlines on-time record100.0%
- United Airlines on-time record90.3%
- SkyWest Airlines on-time record85.6%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to LAX and LAX to SEA 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, June 2025 to May 2026. Updated monthly. How this data is collected.