Route reliability record
SEA→LAS
Seattle to Las Vegas
- Flights
- 5,703
- Period
- June 2025 to May 2026
- Distance
- 867 mi
- Carriers
- 6
This route lands a B+, about a point worse than the national rate of 77.4%. About one flight in four arrive 15 minutes late or worse, and those flights are late by roughly 55 minutes on average. That is a workable record, not a spotless one. That rests on 5,703 flights, of which Delta Air Lines flew 1,735 at 83.5% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 83.5% on time across 1,735 flights.
Key figures
On time
76.6%
Arrivals under 15 minutes late, of 5,640 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
0.95%
National rate is 1.80%
Best carrier
Delta
83.5% on time across 1,735 flights
These figures cover 5,703 flights between June 2025 and May 2026. The median arrival is 3 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 SEA to LAS
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 83.5% of the time; Southwest Airlines manages 68.5%. 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 |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 9 | 100.0% | — | 0.00% | A+ |
| Delta Air Lines | 1,735 | 83.5% | 56 min | 0.98% | B+ |
| Alaska Airlines | 2,661 | 76.1% | 45 min | 0.98% | B+ |
| Spirit Airlinesthin sample | 84 | 68.7% | 38 min | 1.19% | C |
| Southwest Airlines | 977 | 68.5% | 48 min | 0.61% | C+ |
| Frontier Airlinesthin sample | 237 | 67.8% | 131 min | 1.69% | C |
The spread between Delta and Southwest is 15 points, wide enough that it should decide the booking. On a hundred trips that is 15 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 26 points, against 15 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am778 flights91.7%
- 8am–11am1,054 flights84.5%
- 11am–2pm1,045 flights76.5%
- 2pm–5pm1,110 flights70.2%
- 5pm–8pm1,054 flights66.2%
- 8pm–5am662 flights74.1%
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 91.7% of the time, against 66.2% for the evening window. That is 26 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 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.
June is the worst month at 68.4% 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.
Across the week, Saturday is the strongest day at 81.5% on time and Monday the weakest at 73.4%. 8 points is a smaller lever than departure hour, but it is free.
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.
- 40%Carrier
- 34%Late-arriving aircraft
- 24%National Airspace System
- 2%Extreme weather
- 1%Security
The largest share of delay minutes, 40%, 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 28,000 of the 70,000 delay minutes reported here.
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 0.95% against a national 1.80%, which is ordinary. Diversions add another 0.16%.
Connections and stage length
What a delay here actually costs
5.8% of arrivals land an hour or more late, close to the national 8.2%. 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 are the roughly 55 minutes kind, 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 is a different operation and performs like one: it runs 82.0% on time across 5,699 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 5,703 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. April runs 84.4% on time and June 68.4%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else.
Common questions
SEA to LAS questions
How often is SEA to LAS delayed?
About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.4% of the 5,703 flights in this analysis, against 22.6% nationally. Delayed flights are late by roughly 55 minutes on average.
Which airline is most reliable on SEA to LAS?
Delta Air Lines leads at 83.5% on time across 1,735 flights. Southwest Airlines is at the other end on 68.5%, a gap of 15 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 66.2%, 26 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 SEA to LAS?
June is the weakest month at 68.4% 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.
Related
Where to go next
- LAS to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Harry Reid International (LAS) delay statistics
- SkyWest Airlines on-time record100.0%
- Delta Air Lines on-time record83.5%
- Alaska Airlines on-time record76.1%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.