Route reliability record

SEA→LAS

Seattle to Las Vegas

Flights: 5,620
Period: September 2025 to August 2026
Distance: 867 mi
Carriers: 5

This route lands a B+, level with the national rate of 77.3%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 5,620 SEA to LAS flights, of which Delta Air Lines flew 1,748 at 81.3% on time.

Best time to fly SEA to LAS: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 91.7% of the time and Saturday flights 84.2%, against 77.6% for the route overall.

Delta Air Lines is the most reliable of the three carriers covered here at 81.3% on time across 1,748 flights.

On time

77.6%

Arrivals under 15 minutes late, of 5,564 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.93%

National rate is 1.89%

Best carrier

Delta

81.3% on time across 1,748 flights

These figures cover 5,620 flights between September 2025 and August 2026. The median arrival is 4 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.

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Carrier by carrier

Which airline is most reliable on SEA to LAS

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.3% of the time; Southwest Airlines manages 70.3%. 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 SEA to LAS
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlinesthin sample	9	100.0%	—	0.00%	A+
Delta Air Lines	1,748	81.3%	54 min	1.09%	B
Alaska Airlines	2,612	78.7%	48 min	0.84%	B+
Southwest Airlines	977	70.3%	52 min	0.51%	C+
Frontier Airlinesthin sample	274	68.7%	128 min	2.19%	C

Delta leads Southwest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Flights on SEA to LAS

The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.

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Best ways to make this trip

The most reliable ways to fly Seattle to Las Vegas

Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.

Most reliable ways to fly from SEA to LAS
Option	Airline	Success	On time	Cancelled	Best departure	Most punctual flight
1. SEA → LASSeattle to Las Vegas	Delta Air Lines	80.4%	81.3%	1.09%	5am–8am, Sat	DL 2922 07:20
2. SEA → LASSeattle to Las Vegas	Alaska Airlines	78.0%	78.7%	0.84%	5am–8am, Sat	AS 704 08:25
3. SEA → LASSeattle to Las Vegas	Southwest Airlines	69.9%	70.3%	0.51%	5am–8am, Sat	—

Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.

Plan this trip by month, day and time

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 23 points, against 11 points between the best and worst carrier.

5am–8am863 flights91.7%
8am–11am875 flights84.2%
11am–2pm1,140 flights77.7%
2pm–5pm1,077 flights70.3%
5pm–8pm846 flights68.9%
8pm–5am819 flights74.3%

Scale runs 60% to 95%.

Book the early departure. Flights leaving between 5am–8am arrive on time 91.7% of the time, against 68.9% for the evening window. That is 23 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 1,140 flights scheduled in it.

Explore

Filter SEA to LAS by airline, time, month and day

Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.

On SEA to LAS, the best departure window is 5am–8am at 91.7% on time and the worst is 5pm–8pm at 68.9%, a wide gap of 22.8 points. All US flights leaving 5am–8am ran 89.3%.

5–8am91.7%
8–11am84.2%
11am–2pm77.7%
2–5pm70.3%
5–8pm68.9%
8pm–5am74.3%

best all US flightsScale 60% to 95%.

Across the year

When delays peak on this route

This route's year swings by 16 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.April best, August worst

August is the worst month at 68.8% on time, 16 points below April, the best at 84.4%. 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. May was the busiest month here, with 497 flights.

Across the week, Saturday is the strongest day at 84.2% on time and Friday the weakest at 72.5%, a spread of 12 points.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 70,000 reported delay minutes.

Carrier
41%
Late-arriving aircraft
29%
National Airspace System
26%
Extreme weather
2%
Security
1%

The largest share of delay minutes, 41%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 29,000 of the 70,000 delay minutes reported here. The split is drawn from 69,633 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 91.7% on time here.

Cancellations sit at 0.93% against a national 1.89%, which is ordinary. Diversions add another 0.07%.

Connections and stage length

What a delay here actually costs

6.1% of arrivals land an hour or more late, close to the national 8.3%, so 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 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.

The return leg is a different operation and performs like one: it runs 82.1% on time across 5,617 flights, 5 points above 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 5,620 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.

Work out the risk of missing a connection in LAS after this flight

What to do with this

Booking this route

Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 84.4% on time and August 68.8%, a swing of 16 points. If the dates move at all, move them out of August before you think about anything else. 5,564 completed flights over 12 months sit behind that.

Common questions

SEA to LAS questions

How often is SEA to LAS delayed?

Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.4% of the 5,620 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on SEA to LAS?

Delta Air Lines leads at 81.3% on time across 1,748 flights. Southwest Airlines is at the other end on 70.3%, a gap of 11 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 SEA to LAS?

The 5am–8am departure window is the strongest at 91.7% on time. The 5pm–8pm window is the weakest at 68.9%, 23 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 August delays on SEA to LAS?

August is the weakest month at 68.8% on time, compared with 84.4% in April. Across the year that is 16 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. SEA to LAS and LAS to SEA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

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<iframe src="https://delayatlas.com/embed/route/sea-las" width="320" height="132" style="border:0;max-width:100%" loading="lazy" title="SEA to LAS on-time record"></iframe>
<p style="font:12px/1.4 sans-serif;margin:4px 0 0">SEA to LAS flight delay statistics from <a href="https://delayatlas.com/routes/sea-to-las">DelayAtlas</a></p>

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.