Route reliability record

LAX→SEA

Los Angeles to Seattle

Flights: 7,424
Period: July 2025 to June 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 77.6%. When something does go wrong the average delay runs about an hour. That rests on 7,424 flights, of which Delta Air Lines flew 2,224 at 86.8% on time.

Delta Air Lines is the most reliable of the four carriers covered here at 86.8% on time across 2,224 flights.

On time

85.4%

Arrivals under 15 minutes late, of 7,342 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

0.98%

National rate is 1.81%

Best carrier

Delta

86.8% on time across 2,224 flights

These figures cover 7,424 flights between July 2025 and June 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: 2 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.

On-time performance by carrier on LAX to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	2,224	86.8%	76 min	0.76%	A+
Alaska Airlines	3,279	85.2%	49 min	1.10%	A
United Airlines	395	85.0%	47 min	0.51%	A+
SkyWest Airlines	1,239	84.6%	82 min	0.65%	B+
American Airlinesthin sample	11	81.8%	159 min	0.00%	B+
Frontier Airlinesthin sample	276	79.7%	76 min	3.62%	B−

No carrier stands out. Delta tops the table at 86.8%, 2 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 7,424 flights.

5am–8am817 flights90.6%
8am–11am1,295 flights89.2%
11am–2pm1,207 flights84.6%
2pm–5pm1,460 flights83.6%
5pm–8pm1,851 flights83.0%
8pm–5am794 flights83.4%

Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.

The early departures do better, though not dramatically: 90.6% on time for the 5am–8am window against 83.0% for 5pm–8pm. Worth taking if the schedule allows, not worth an extra connection. The 5pm–8pm window is the busiest, with 1,851 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 14 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.

Darker means more delays. Figures are on-time percentages.September best, June worst

June is the worst month at 78.7% on time, 14 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. May was the busiest month here, with 679 flights.

Across the week, Tuesday is the strongest day at 88.7% on time and Friday the weakest at 80.9%. 8 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 52% 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.

Carrier
52%
Late-arriving aircraft
33%
National Airspace System
14%
Extreme weather
1%
Security
0%

The largest share of delay minutes, 52%, 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 split is drawn from 68,457 reported delay minutes.

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 0.98% against a national 1.81%, which is ordinary. Diversions add another 0.12%.

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 8.1% 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 83.4% on time across 7,428 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 7,424 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 78.7%, a swing of 14 points. If the dates move at all, move them out of June before you think about anything else. 7,342 completed flights over 12 months sit behind that.

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 14.6% of the 7,424 flights in this analysis, against 22.4% 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 86.8% on time across 2,224 flights. SkyWest Airlines is at the other end on 84.6%, a gap of 2 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 5pm–8pm window is the weakest at 83.0%, 8 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 78.7% on time, compared with 92.5% in September. Across the year that is 14 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures