Carrier route record
ASBOS→SAN
Alaska Airlines · Boston to San Diego
- Flights
- 508
- Period
- July 2025 to June 2026
- Share of route
- 28%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on BOS to SAN sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 508 flights, with a median arrival 1 minute early.
The national on-time rate over the same period is 77.6%, so Alaska on BOS to SAN runs 8 points behind the country as a whole. Across a thousand flights that is about 78 extra late arrivals.
Key figures
On time
69.8%
Arrivals under 15 minutes late, of 496 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
1.57%
National rate is 1.81%
Whole route
76.5%
Every carrier on BOS to SAN, 1,818 flights
These figures cover 508 flights between July 2025 and June 2026. Beyond the headline rate, 8.3% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Alaska against every carrier on BOS to SAN
Alaska flew 508 of the 1,818 flights on BOS to SAN, about 28% of it. Its 69.8% on time is 7 points worse than the route as a whole, which runs 76.5%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from JetBlue at 84.9% to Southwest at 29.6%. 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 |
|---|---|---|---|---|---|
| JetBlue Airways | 919 | 84.9% | 64 min | 1.20% | B |
| Alaska Airlines (this page) | 508 | 69.8% | 56 min | 1.57% | C |
| Delta Air Linesthin sample | 364 | 67.9% | 43 min | 1.65% | C |
| Southwest Airlinesthin sample | 27 | 29.6% | 72 min | 0.00% | F+ |
Flight by flight
Alaska flight numbers on BOS to SAN
Departure window
When Alaska runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 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–8am64 flights68.9%
- 8am–11am120 flights83.8%
- 11am–2pm—
- 2pm–5pm119 flights73.0%
- 5pm–8pm205 flights60.1%
- 8pm–5am—
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 60.1% on time, against 83.8% 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 5pm–8pm window is the busiest, with 205 flights scheduled in it.
Across the year
Alaska on BOS to SAN through the year
July is the worst month at 57.6% on time, 22 points below April, the best at 80.0%. 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. July was the busiest month here, with 61 flights.
Across the week, Wednesday is the strongest day at 73.8% on time and Friday the weakest at 62.7%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Alaska runs late on this route
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 8,385 reported delay minutes.
- 36%National Airspace System
- 32%Late-arriving aircraft
- 29%Carrier
- 2%Extreme weather
- 0%Security
36% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 3,030 minutes out of 8,385, against a national NAS share of 21%. The split is drawn from 8,385 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 83.8% on time here.
Cancellations sit at 1.57% against a national 1.81%, which is ordinary. Diversions add another 0.79%.
Connections and stage length
What a delay here costs
8.3% 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 about an hour, which a normal layover absorbs.
At 2,588 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 76.2% on time across 508 flights, 6 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 6 points of difference.
One caution: this is a thin sample. 508 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 Alaska on BOS to SAN
Put together: treat all of this as provisional. 508 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 69.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 496 completed flights over 12 months sit behind that.
Related
Where to go next
- BOS to SAN, every carrier
- Alaska on SAN to BOS, the return leg
- JetBlue Airways on BOS to SAN84.9%
- Delta Air Lines on BOS to SAN67.9%
- Alaska Airlines network-wide record
- Boston Logan International (BOS) delay statistics
- 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 7.04 million flight records
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.