Route reliability record
LAS→SEA
Las Vegas to Seattle
- Flights
- 5,649
- Period
- July 2025 to June 2026
- Distance
- 867 mi
- Carriers
- 6
This route lands a B+, 5 points better than the national rate of 77.6%. 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 5,649 flights, of which Delta Air Lines flew 1,738 at 87.6% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 87.6% on time across 1,738 flights.
Key figures
On time
82.3%
Arrivals under 15 minutes late, of 5,590 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
0.94%
National rate is 1.81%
Best carrier
Delta
87.6% on time across 1,738 flights
These figures cover 5,649 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
Which airline is most reliable on LAS to SEA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 87.6% of the time; Southwest Airlines manages 71.0%. Sample sizes sit next to every figure, because a two-point gap across 977 flights means less than a ten-point one.
| 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 | 977 | 71.0% | 45 min | 0.31% | C+ |
The spread between Delta and Southwest is 17 points, wide enough that it should decide the booking. On a hundred trips that is 17 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 17 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,020 flights91.5%
- 8am–11am924 flights85.0%
- 11am–2pm1,177 flights86.6%
- 2pm–5pm1,051 flights76.9%
- 5pm–8pm998 flights76.1%
- 8pm–5am479 flights71.0%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.5% of the time, against 71.0% 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. The 11am–2pm window is the busiest, with 1,177 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 17 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.
August is the worst month at 76.5% on time, 17 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. July was the busiest month here, with 521 flights.
Across the week, Tuesday is the strongest day at 86.4% on time and Friday the weakest at 76.1%. 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 46% 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.
- 46%Late-arriving aircraft
- 37%Carrier
- 15%National Airspace System
- 3%Extreme weather
- 0%Security
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 62,000 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 62,284 reported delay minutes.
The largest share of delay minutes, 37%, 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 23,000 of the 62,000 delay minutes reported here.
Cancellations sit at 0.94% against a national 1.81%, which is ordinary. Diversions add another 0.11%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.6% 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 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 77.7% on time across 5,650 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 5,649 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 August 76.5%, a swing of 17 points. If the dates move at all, move them out of August before you think about anything else. 5,590 completed flights over 12 months sit behind that.
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 17.7% of the 5,649 flights in this analysis, against 22.4% 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 87.6% on time across 1,738 flights. Southwest Airlines is at the other end on 71.0%, a gap of 17 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 91.5% on time. The 8pm–5am window is the weakest at 71.0%, 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 August delays on LAS to SEA?
August is the weakest month at 76.5% on time, compared with 93.4% in February. Across the year that is 17 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SEA to LAS — the return legseparate record
- Harry Reid International (LAS) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Spirit Airlines on-time record88.4%
- Delta Air Lines on-time record87.6%
- SkyWest Airlines on-time record85.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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, July 2025 to June 2026. Updated monthly. How this data is collected.