Carrier route record

DLSEA→LAX

Delta Air Lines · Seattle to Los Angeles

Flights: 2,225
Period: July 2025 to June 2026
Share of route: 30%
Carriers: 6

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on SEA to LAX 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 77.6%. When something does go wrong the average delay runs about an hour. That rests on 2,225 flights. The strongest carrier on the route with a full sample, United Airlines, flew 393 at 90.3% on time.

United Airlines is the most reliable of the three carriers covered here at 90.3% on time across 393 flights.

On time

84.5%

Arrivals under 15 minutes late, of 2,209 completed flights

Avg delay

59 min

Across delayed arrivals only, not all flights

Cancelled

0.67%

National rate is 1.81%

Whole route

83.4%

Every carrier on SEA to LAX, 7,428 flights

These figures cover 2,225 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

Delta against every carrier on SEA to LAX

Delta flew 2,225 of the 7,428 flights on SEA to LAX, about 30% of it. Its 84.5% on time is about level with the route as a whole at 83.4%. Ranked by on-time rate it is number four of six carriers on the route, where the range runs from American at 90.9% to Frontier at 78.9%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. United Airlines arrives on time 90.3% of the time; Alaska Airlines manages 81.0%. Sample sizes sit next to every figure, because a two-point gap across 3,282 flights means less than a ten-point one.

On-time performance by carrier on SEA to LAX
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlinesthin sample	11	90.9%	149 min	0.00%	A+
United Airlines	393	90.3%	98 min	0.00%	A+
SkyWest Airlines	1,241	86.3%	109 min	0.64%	A+
Delta Air Lines (this page)	2,225	84.5%	59 min	0.67%	B+
Alaska Airlines	3,282	81.0%	43 min	1.07%	B
Frontier Airlinesthin sample	276	78.9%	60 min	3.62%	B−

United leads Alaska by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Delta flight numbers on SEA to LAX

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 14 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am361 flights93.1%
8am–11am353 flights86.7%
11am–2pm437 flights82.4%
2pm–5pm275 flights87.5%
5pm–8pm407 flights78.9%
8pm–5am392 flights80.5%

Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.1% of the time, against 78.9% for the evening window. That is 14 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 437 flights scheduled in it.

Across the year

Delta on SEA to LAX through the year

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

December is the weak month at 75.2% on time, against 92.2% 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. May was the busiest month here, with 204 flights.

Across the week, Saturday is the strongest day at 87.7% on time and Thursday the weakest at 81.4%. 6 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 53% of the 20,000 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
53%
Late-arriving aircraft
30%
National Airspace System
15%
Extreme weather
2%

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 11,000 of the 20,000 delay minutes reported here. The split is drawn from 20,378 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 93.1% on time here.

Cancellations are rare at 0.67%, below the national 1.81% 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 costs

Badly late arrivals are rare here: only 4.2% 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 86.8% on time across 2,224 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 2,225 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 Delta on SEA to LAX

Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 92.2% on time and December 75.2%, a swing of 17 points. If the dates move at all, move them out of December before you think about anything else. 2,209 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures