Carrier route record
WNLAS→SEA
Southwest Airlines · Las Vegas to Seattle
- Flights
- 977
- Period
- July 2025 to June 2026
- Share of route
- 17%
- Carriers
- 6
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on LAS to SEA sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land about 45 minutes behind schedule. That rests on 977 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,738 at 87.6% on time.
The national on-time rate over the same period is 77.6%, so Southwest on LAS to SEA runs 7 points behind the country as a whole. Across a thousand flights that is about 66 extra late arrivals.
Key figures
On time
71.0%
Arrivals under 15 minutes late, of 972 completed flights
Avg delay
45 min
Across delayed arrivals only, not all flights
Cancelled
0.31%
National rate is 1.81%
Whole route
82.3%
Every carrier on LAS to SEA, 5,649 flights
These figures cover 977 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
Carrier by carrier
Southwest against every carrier on LAS to SEA
Southwest flew 977 of the 5,649 flights on LAS to SEA, about 17% of it. Its 71.0% on time is 11 points worse than the route as a whole, which runs 82.3%. Ranked by on-time rate it is last of six carriers on the route, where the range runs from Spirit at 88.4% to Southwest at 71.0%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 5 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 43 | 88.4% | 47 min | 0.00% | A+ |
| Delta Air Lines | 1,738 | 87.6% | 87 min | 0.86% | A+ |
| SkyWest Airlinesthin sample | 7 | 85.7% | 59 min | 0.00% | A+ |
| Alaska Airlines | 2,638 | 82.8% | 64 min | 1.25% | B |
| Frontier Airlinesthin sample | 246 | 82.2% | 48 min | 0.81% | B+ |
| Southwest Airlines (this page) | 977 | 71.0% | 45 min | 0.31% | C+ |
No carrier stands out. Delta tops the table at 87.6%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 37 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am95 flights78.7%
- 8am–11am205 flights86.3%
- 11am–2pm81 flights81.5%
- 2pm–5pm142 flights49.6%
- 5pm–8pm138 flights62.0%
- 8pm–5am316 flights69.5%
Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 86.3% of the time, against 49.6% for the afternoon window. That is 37 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 316 flights scheduled in it.
Across the year
Southwest on LAS to SEA through the year
June is the worst month at 54.4% on time, 39 points below February, the best at 93.0%. 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 93 flights.
Across the week, Tuesday is the strongest day at 78.8% on time and Friday the weakest at 62.6%. 16 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 54% of the 13,000 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.
- 54%Late-arriving aircraft
- 33%Carrier
- 10%National Airspace System
- 3%Extreme weather
54% 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 13,000 reported delay minutes here, that single category outweighs weather by 18 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 12,656 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 86.3% on time here.
Cancellations are rare at 0.31%, 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
5.9% 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 45 minutes, 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. 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 69.2% on time across 976 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.
One caution: this is a thin sample. 977 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 Southwest on LAS to SEA
Put together: treat all of this as provisional. 977 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 71.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 972 completed flights over 12 months sit behind that.
Related
Where to go next
- LAS to SEA, every carrier
- Southwest on SEA to LAS, the return leg
- Delta Air Lines on LAS to SEA87.6%
- Alaska Airlines on LAS to SEA82.8%
- Frontier Airlines on LAS to SEA82.2%
- Southwest Airlines network-wide record
- Harry Reid International (LAS) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.