Route reliability record

LAS→SEA

Las Vegas to Seattle

Flights: 5,699
Period: June 2025 to May 2026
Distance: 867 mi
Carriers: 6

This route lands a B, 5 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 5,699 flights, of which Delta Air Lines flew 1,735 at 87.9% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 87.9% on time across 1,735 flights.

On time

82.0%

Arrivals under 15 minutes late, of 5,637 completed flights

Avg delay

61 min

Across delayed arrivals only, not all flights

Cancelled

1.02%

National rate is 1.80%

Best carrier

Delta

87.9% on time across 1,735 flights

These figures cover 5,699 flights between June 2025 and May 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

Which airline is most reliable on LAS to SEA

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 87.9% of the time; Southwest Airlines manages 71.6%. Sample sizes sit next to every figure, because a two-point gap across 977 flights means less than a ten-point one.

On-time performance by carrier on LAS to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,735	87.9%	87 min	0.98%	A+
SkyWest Airlinesthin sample	7	85.7%	59 min	0.00%	A+
Spirit Airlinesthin sample	83	85.5%	52 min	0.00%	A+
Alaska Airlines	2,660	82.0%	60 min	1.28%	B
Frontier Airlinesthin sample	237	79.8%	55 min	1.27%	B
Southwest Airlines	977	71.6%	45 min	0.41%	C+

The spread between Delta and Southwest is 16 points, wide enough that it should decide the booking. On a hundred trips that is 16 more arrivals inside the on-time window.

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 21 points, against 16 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am958 flights91.9%
8am–11am990 flights84.0%
11am–2pm1,138 flights85.7%
2pm–5pm1,087 flights77.2%
5pm–8pm1,029 flights77.2%
8pm–5am497 flights70.6%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 91.9% of the time, against 70.6% for the overnight window. That is 21 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 18 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.February best, June worst

June is the worst month at 75.0% on time, 18 points below February, the best at 93.4%. 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, Wednesday is the strongest day at 86.6% on time and Friday the weakest at 76.6%. 10 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. Late-arriving aircraft accounts for 47% of the 62,000 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.

Late-arriving aircraft
47%
Carrier
34%
National Airspace System
17%
Extreme weather
3%
Security
0%

47% 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 62,000 reported delay minutes here, that single category outweighs weather by 17 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 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 91.9% on time here.

Cancellations sit at 1.02% against a national 1.80%, which is ordinary. Diversions add another 0.07%.

Connections and stage length

What a delay here actually costs

Badly late arrivals are rare here: only 4.7% 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 867 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 is a different operation and performs like one: it runs 76.6% on time across 5,703 flights, 5 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.

The sample behind these figures is 5,699 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. February runs 93.4% on time and June 75.0%, a swing of 18 points. If the dates move at all, move them out of June before you think about anything else.

Common questions

LAS to SEA questions

How often is LAS to SEA 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 18.0% of the 5,699 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on LAS to SEA?

Delta Air Lines leads at 87.9% on time across 1,735 flights. Southwest Airlines is at the other end on 71.6%, a gap of 16 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 LAS to SEA?

The 5am–8am departure window is the strongest at 91.9% on time. The 8pm–5am window is the weakest at 70.6%, 21 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 LAS to SEA?

June is the weakest month at 75.0% on time, compared with 93.4% in February. Across the year that is 18 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. LAS to SEA and SEA to LAS 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.

Key figures