Carrier route record
WNBOI→SAN
Southwest Airlines · Boise to San Diego
- 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 BOI to SAN sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.3%. The late ones land roughly 50 minutes behind schedule. That rests on 426 flights, with a median arrival 3 minutes early.
The US average over the same twelve months is 77.3%, so there is little to separate Southwest on BOI to SAN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
74.4%
Arrivals under 15 minutes late, of 422 completed flights
Avg delay
48 min
Across delayed arrivals only, not all flights
Cancelled
0.47%
National rate is 1.89%
Whole route
79.9%
Every carrier on BOI to SAN, 1,033 flights
These figures cover 426 flights between September 2025 and August 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.
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Carrier by carrier
Southwest against every carrier on BOI to SAN
Southwest flew 426 of the 1,033 flights on BOI to SAN, about 41% of it. Its 74.4% on time is 6 points worse than the route as a whole, which runs 79.9%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Alaska at 90.0% to Southwest at 74.4%. 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 |
|---|---|---|---|---|---|
| Alaska Airlinesthin sample | 252 | 90.0% | 33 min | 1.19% | A |
| SkyWest Airlinesthin sample | 355 | 79.4% | 58 min | 0.85% | B+ |
| Southwest Airlines (this page) | 426 | 74.4% | 48 min | 0.47% | C+ |
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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 54 points, against half a point between the best and worst carrier.
- 5am–8am106 flights93.3%
- 8am–11am24 flights—
- 11am–2pm128 flights80.5%
- 2pm–5pm94 flights65.6%
- 5pm–8pm43 flights39.0%
- 8pm–5am31 flights41.9%
Scale runs 30% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 39.0% on time, against 93.3% 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 128 flights scheduled in it.
Across the year
Southwest on BOI to SAN through the year
July is the worst month at 63.3% on time, 27 points below April, the best at 90.0%. 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. August was the busiest month here, with 61 flights.
Across the week, Saturday is the strongest day at 93.0% on time and Thursday the weakest at 69.9%, a spread of 23 points.
Arrival by arrival
How late Southwest on BOI to SAN runs when it is late
The 108 late arrivals split 50 under half an hour, 32 between 30 and 60 minutes, and 26 an hour or more.
- 15+ min early66 flights15.6%
- Within 15 min248 flights58.8%
- 15–29 min late50 flights11.8%
- 30–59 min late32 flights7.6%
- 1–2 hours late20 flights4.7%
- 2+ hours late6 flights1.4%
Scale runs 0% to 100%.
Share of 422 completed flights by arrival against schedule.
23 of 118 late departures made up the time and arrived on time, 19% of them. 13 flights left on time and still arrived late.
The worst days
Worst days for Southwest on BOI to SAN
The latest arrival of the period was on 21 November 2025, 5 hours 18 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 21 November 2025 | 5 hours 18 minutes | Late-arriving aircraft |
| 17 February 2026 | 4 hours 15 minutes | Late-arriving aircraft |
| 4 September 2025 | 4 hours 10 minutes | Carrier |
| 12 April 2026 | 2 hours 32 minutes | Late-arriving aircraft |
| 27 July 2026 | 2 hours 9 minutes | Carrier |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 53% of the 5,174 delay minutes carriers reported here, and the remaining four split what is left.
- 53%Late-arriving aircraft
- 24%Carrier
- 23%National Airspace System
53% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,174 reported delay minutes here, that single category outweighs weather by 53 to one. The split is drawn from 5,174 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 93.3% on time here.
Cancellations are rare at 0.47%, below the national 1.89% 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
6.2% 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 roughly 50 minutes, 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 73.0% 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 BOI to SAN
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 74.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 422 completed flights over 12 months sit behind that.
Related
Where to go next
- BOI to SAN, every carrier
- Southwest on SAN to BOI, the return leg
- Alaska Airlines on BOI to SAN90.0%
- SkyWest Airlines on BOI to SAN79.4%
- 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.