Carrier route record
ASSAN→BOS
Alaska Airlines · San Diego to Boston
- 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 SAN to BOS lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 508 flights, with a median arrival 2 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate Alaska on SAN to BOS from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.2%
Arrivals under 15 minutes late, of 492 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
1.77%
National rate is 1.81%
Whole route
77.9%
Every carrier on SAN to BOS, 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 SAN to BOS
Alaska flew 508 of the 1,818 flights on SAN to BOS, about 28% of it. Its 76.2% on time is 2 points worse than the route as a whole, which runs 77.9%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from JetBlue at 79.3% to Southwest at 44.4%. 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 |
|---|---|---|---|---|---|
| JetBlue Airways | 919 | 79.3% | 99 min | 1.41% | B |
| Delta Air Linesthin sample | 364 | 79.3% | 86 min | 1.65% | B |
| Alaska Airlines (this page) | 508 | 76.2% | 66 min | 1.77% | B |
| Southwest Airlinesthin sample | 27 | 44.4% | 69 min | 0.00% | F+ |
Flight by flight
Alaska flight numbers on SAN to BOS
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 23 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–8am49 flights93.9%
- 8am–11am309 flights71.0%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm—
- 8pm–5am150 flights80.8%
Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.9% of the time, against 71.0% for the morning window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 309 flights scheduled in it.
Across the year
Alaska on SAN to BOS through the year
July is the worst month at 65.5% on time, 27 points below May, the best at 92.0%. 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, Saturday is the strongest day at 85.5% on time and Wednesday the weakest at 71.4%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Alaska runs late on this route
One category carries most of the weight here. National Airspace System accounts for 49% of the 7,739 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.
- 49%National Airspace System
- 25%Late-arriving aircraft
- 19%Extreme weather
- 6%Carrier
Extreme weather accounts for 19% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 3.1 times the usual weather exposure. The split is drawn from 7,739 reported delay minutes.
49% 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 3,813 minutes out of 7,739, against a national NAS share of 21%.
Cancellations sit at 1.77% against a national 1.81%, which is ordinary. Diversions add another 1.38%.
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 69.8% on time across 508 flights, 6 points below 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 SAN to BOS
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 76.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 492 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to BOS, every carrier
- Alaska on BOS to SAN, the return leg
- JetBlue Airways on SAN to BOS79.3%
- Delta Air Lines on SAN to BOS79.3%
- Alaska Airlines network-wide record
- San Diego International (SAN) delay statistics
- Boston Logan International (BOS) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
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.