Carrier route record

WNLAS→BOI

Southwest Airlines · Las Vegas to Boise

Flights: 1,049
Period: July 2025 to June 2026
Share of route: 75%
Carriers: 5

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on LAS to BOI sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 1,049 flights, with a median arrival 2 minutes early.

The national on-time rate over the same period is 77.6%, so Southwest on LAS to BOI runs 5 points behind the country as a whole. Across a thousand flights that is about 51 extra late arrivals.

On time

72.5%

Arrivals under 15 minutes late, of 1,048 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

0.10%

National rate is 1.81%

Whole route

73.3%

Every carrier on LAS to BOI, 1,400 flights

These figures cover 1,049 flights between July 2025 and June 2026. The median arrival is 2 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

Southwest against every carrier on LAS to BOI

Southwest flew 1,049 of the 1,400 flights on LAS to BOI, most of the route. Its 72.5% on time is about level with the route as a whole at 73.3%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from Alaska at 85.9% to Spirit at 66.0%. Four of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on LAS to BOI
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlinesthin sample	71	85.9%	104 min	0.00%	A+
SkyWest Airlinesthin sample	219	74.8%	78 min	0.46%	C+
Southwest Airlines (this page)	1,049	72.5%	49 min	0.10%	C+
Allegiant Airthin sample	14	71.4%	78 min	0.00%	C+
Spirit Airlinesthin sample	47	66.0%	80 min	0.00%	C+

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 28 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am25 flights—
8am–11am327 flights87.8%
11am–2pm29 flights—
2pm–5pm269 flights67.5%
5pm–8pm142 flights63.4%
8pm–5am257 flights60.3%

Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 60.3% on time, against 87.8% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 327 flights scheduled in it.

Across the year

Southwest on LAS to BOI through the year

Darker means more delays. Figures are on-time percentages.August best, June worst

June is the worst month at 52.3% on time, 34 points below August, the best at 86.1%. 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. December was the busiest month here, with 96 flights.

Across the week, Tuesday is the strongest day at 80.7% on time and Sunday the weakest at 65.6%. 15 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 60% 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.

Late-arriving aircraft
60%
Carrier
34%
National Airspace System
6%
Extreme weather
0%

60% 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 60 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 13,203 reported delay minutes.

The largest share of delay minutes, 34%, 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 4,506 of the 13,000 delay minutes reported here.

Cancellations are rare at 0.10%, 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

6.7% 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 roughly 50 minutes, which a normal layover absorbs.

The 519 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 81.6% on time across 1,050 flights, 9 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 9 points of difference.

One caution: this is a thin sample. 1,049 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 BOI

Put together: treat all of this as provisional. 1,049 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 72.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,048 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures