Route reliability record
LAX→SEA
Los Angeles to Seattle
- Flights
- 7,405
- Period
- June 2025 to May 2026
- Distance
- 954 mi
- Carriers
- 6
This route earns a 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 77.4%. When something does go wrong the average delay runs about an hour. That rests on 7,405 flights, of which Delta Air Lines flew 2,222 at 87.3% on time.
Delta Air Lines is the most reliable of the four carriers covered here at 87.3% on time across 2,222 flights.
Key figures
On time
85.2%
Arrivals under 15 minutes late, of 7,321 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
1.03%
National rate is 1.80%
Best carrier
Delta
87.3% on time across 2,222 flights
These figures cover 7,405 flights between June 2025 and May 2026. The median arrival is 11 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 LAX to SEA
The four carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Delta Air Lines | 2,222 | 87.3% | 75 min | 0.72% | A+ |
| Alaska Airlines | 3,280 | 84.8% | 50 min | 1.22% | B |
| SkyWest Airlines | 1,246 | 84.2% | 82 min | 0.64% | B+ |
| United Airlines | 395 | 84.0% | 44 min | 0.51% | B+ |
| Frontier Airlinesthin sample | 261 | 80.1% | 75 min | 3.83% | B− |
No carrier stands out. Delta tops the table at 87.3%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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 7,405 flights.
- 5am–8am812 flights90.6%
- 8am–11am1,295 flights88.7%
- 11am–2pm1,194 flights84.8%
- 2pm–5pm1,420 flights84.1%
- 5pm–8pm1,856 flights83.1%
- 8pm–5am828 flights82.0%
Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.6% of the time, against 82.0% for the overnight window. That is 9 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 15 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 77.2% on time, 15 points below September, the best at 92.5%. 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.
Across the week, Tuesday is the strongest day at 89.1% on time and Friday the weakest at 80.2%. 9 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 51% of the 68,000 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.
- 51%Carrier
- 32%Late-arriving aircraft
- 15%National Airspace System
- 1%Extreme weather
- 0%Security
The largest share of delay minutes, 51%, 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 35,000 of the 68,000 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 90.6% on time here.
Cancellations sit at 1.03% against a national 1.80%, which is ordinary. Diversions add another 0.11%.
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 83.0% on time across 7,410 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 7,405 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 92.5% on time and June 77.2%, a swing of 15 points. If the dates move at all, move them out of June before you think about anything else.
Common questions
LAX to SEA questions
How often is LAX to SEA delayed?
About one flight in seven arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 14.8% of the 7,405 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on LAX to SEA?
Delta Air Lines leads at 87.3% on time across 2,222 flights. United Airlines is at the other end on 84.0%, a gap of 3 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 LAX to SEA?
The 5am–8am departure window is the strongest at 90.6% on time. The 8pm–5am window is the weakest at 82.0%, 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 LAX to SEA?
June is the weakest month at 77.2% on time, compared with 92.5% in September. Across the year that is 15 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
- SEA to LAX — the return legseparate record
- Los Angeles International (LAX) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- American Airlines on-time record100.0%
- Delta Air Lines on-time record87.3%
- Alaska Airlines on-time record84.8%
- 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. LAX to SEA and SEA to LAX 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.