Carrier route record
WNSAN→BOI
Southwest Airlines · San Diego to Boise
- Flights
- 426
- Period
- September 2025 to August 2026
- Share of route
- 41%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SAN to BOI sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 426 flights, with a median arrival 1 minute early.
The national on-time rate over the same period is 77.3%, so Southwest on SAN to BOI runs 4 points behind the country as a whole. Across a thousand flights that is about 43 extra late arrivals.
Key figures
On time
73.0%
Arrivals under 15 minutes late, of 426 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
Whole route
78.8%
Every carrier on SAN to BOI, 1,035 flights
These figures cover 426 flights between September 2025 and August 2026. Beyond the headline rate, 8.7% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Southwest against every carrier on SAN to BOI
Southwest flew 426 of the 1,035 flights on SAN to BOI, about 41% of it. Its 73.0% on time is 6 points worse than the route as a whole, which runs 78.8%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 83.9% to Southwest at 73.0%. Two 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 356 | 83.9% | 72 min | 0.28% | B+ |
| Alaska Airlinesthin sample | 253 | 81.2% | 45 min | 1.19% | B |
| Southwest Airlines (this page) | 426 | 73.0% | 55 min | 0.00% | C+ |
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
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 30 points, against half a point between the best and worst carrier.
- 5am–8am35 flights88.6%
- 8am–11am85 flights84.7%
- 11am–2pm114 flights71.1%
- 2pm–5pm85 flights70.6%
- 5pm–8pm63 flights58.7%
- 8pm–5am44 flights68.2%
Scale runs 50% to 95%.
The 5pm–8pm window is where this operation falls apart: 58.7% on time, against 88.6% for the 5am–8am 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 11am–2pm window is the busiest, with 114 flights scheduled in it.
Across the year
Southwest on SAN to BOI through the year
Delays peak in May, when the on-time rate falls to 48.7%. July is the strongest month at 87.8%. Moving a flexible trip across that boundary buys 39 points. August was the busiest month here, with 61 flights.
Across the week, Saturday is the strongest day at 84.1% on time and Thursday the weakest at 62.2%, a spread of 22 points.
Arrival by arrival
How late Southwest on SAN to BOI runs when it is late
The 115 late arrivals split 32 under half an hour, 46 between 30 and 60 minutes, and 37 an hour or more.
- 15+ min early87 flights20.4%
- Within 15 min224 flights52.6%
- 15–29 min late32 flights7.5%
- 30–59 min late46 flights10.8%
- 1–2 hours late28 flights6.6%
- 2+ hours late9 flights2.1%
Scale runs 0% to 100%.
Share of 426 completed flights by arrival against schedule.
A late pushback is often recovered here: of 152 departures that left 15 minutes late or more, 46 still arrived on time. 9 flights left on time and still arrived late.
The worst days
Worst days for Southwest on SAN to BOI
The latest arrival of the period was on 19 December 2025, 4 hours 19 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 19 December 2025 | 4 hours 19 minutes | Late-arriving aircraft |
| 9 August 2026 | 4 hours 13 minutes | Late-arriving aircraft |
| 18 September 2025 | 2 hours 57 minutes | Late-arriving aircraft |
| 1 May 2026 | 2 hours 23 minutes | Late-arriving aircraft |
| 21 November 2025 | 2 hours 20 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 78% of the 6,344 delay minutes carriers reported here, and the remaining four split what is left.
- 78%Late-arriving aircraft
- 16%Carrier
- 5%National Airspace System
- 0%Extreme weather
78% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 6,344 reported delay minutes here, that single category outweighs weather by 78 to one. The split is drawn from 6,344 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 88.6% on time here.
Cancellations are rare at 0.00%, below the national 1.89% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
8.7% 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 749 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 runs 74.4% on time across 426 flights, within about a point 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. 426 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 SAN to BOI
Put together: treat all of this as provisional. 426 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 73.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 426 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to BOI, every carrier
- Southwest on BOI to SAN, the return leg
- SkyWest Airlines on SAN to BOI83.9%
- Alaska Airlines on SAN to BOI81.2%
- Southwest Airlines network-wide record
- San Diego International (SAN) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.