Carrier route record

F9SEA→LAX

Frontier Airlines · Seattle to Los Angeles

Flights: 276
Period: July 2025 to June 2026
Share of route: 4%
Carriers: 6

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

Frontier on SEA to LAX lands a B−, about a point better than the national rate of 77.6%. About one flight in five arrives 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 276 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 four carriers covered here at 90.3% on time across 393 flights.

On time

78.9%

Arrivals under 15 minutes late, of 266 completed flights

Avg delay

60 min

Across delayed arrivals only, not all flights

Cancelled

3.62%

National rate is 1.81%

Whole route

83.4%

Every carrier on SEA to LAX, 7,428 flights

These figures cover 276 flights between July 2025 and June 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.

Carrier by carrier

Frontier against every carrier on SEA to LAX

Frontier flew 276 of the 7,428 flights on SEA to LAX, about 4% of it. Its 78.9% on time is 5 points worse than the route as a whole, which runs 83.4%. Ranked by on-time rate it is last of six carriers on the route, where the range runs from American at 90.9% to Frontier at 78.9%. One 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	2,225	84.5%	59 min	0.67%	B+
Alaska Airlines	3,282	81.0%	43 min	1.07%	B
Frontier Airlines (this page)thin 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.

Departure window

When Frontier runs best on this route

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 276 flights.

5am–8am19 flights—
8am–11am66 flights78.1%
11am–2pm102 flights82.2%
2pm–5pm23 flights—
5pm–8pm59 flights80.7%
8pm–5am7 flights—

Scale runs 70% to 90%. Rows with fewer than 30 flights show a dash.

The 11am–2pm window is the strongest at 82.2% on time. The full set of windows spans 4 points.

Across the year

Frontier on SEA to LAX through the year

Jul–Sep 202551 flights72.0%
Oct–Dec 202568 flights73.0%
Jan–Mar 202666 flights85.7%
Apr–Jun 202691 flights82.2%

Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 78.9% on time across 276 flights.

Frontier on SEA to LAX did not run the same all year. Its best quarter was Jan–Mar 2026 at 85.7% on time and its weakest Jul–Sep 2025 at 72.0%, a swing of 14 points on roughly 69 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Thursday is the strongest day at 88.1% on time and Friday the weakest at 68.8%. 19 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Frontier runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 3,377 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.

Late-arriving aircraft
46%
Carrier
38%
National Airspace System
15%
Extreme weather
1%

46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 3,377 reported delay minutes here, that single category outweighs weather by 38 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 3,377 reported delay minutes.

The largest share of delay minutes, 38%, 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 1,272 of the 3,377 delay minutes reported here.

Cancellations run at 3.62%, against 1.81% nationally. That is about one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here costs

7.1% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

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 79.7% on time across 276 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 276 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Frontier on SEA to LAX

Put together: the delay figures matter less here than the 3.62% cancellation rate. A late arrival costs you about an hour; a cancelled flight costs you the day. Book the 11am–2pm departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 266 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