Carrier route record

ASSAN→BOS

Alaska Airlines · San Diego to Boston

Flights: 509
Period: September 2025 to August 2026
Share of route: 27%
Carriers: 4

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.

Alaska on SAN to BOS lands a B, about a point better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 509 flights, with a median arrival 5 minutes early.

The US average over the same twelve months is 77.3%, 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.

On time

78.3%

Arrivals under 15 minutes late, of 494 completed flights

Avg delay

72 min

Across delayed arrivals only, not all flights

Cancelled

1.38%

National rate is 1.89%

Whole route

75.5%

Every carrier on SAN to BOS, 1,881 flights

These figures cover 509 flights between September 2025 and August 2026. Beyond the headline rate, 8.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally.

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Carrier by carrier

Alaska against every carrier on SAN to BOS

Alaska flew 509 of the 1,881 flights on SAN to BOS, about 27% of it. Its 78.3% on time is 3 points better than the route as a whole, which runs 75.5%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from Alaska at 78.3% to Southwest at 38.2%. 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.

On-time performance by carrier on SAN to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines (this page)	509	78.3%	72 min	1.38%	B
Delta Air Linesthin sample	364	78.2%	91 min	1.65%	B
JetBlue Airways	919	76.6%	92 min	2.07%	B
Southwest Airlinesthin sample	89	38.2%	73 min	0.00%	F+

Flight by flight

Alaska flight numbers on SAN to BOS

AS 39007:0076.5% · 358 flights

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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 11 points, against half a point between the best and worst carrier.

5am–8am98 flights84.5%
8am–11am260 flights73.4%
11am–2pm—
2pm–5pm—
5pm–8pm—
8pm–5am151 flights82.6%

Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 84.5% of the time, against 73.4% for the morning window. That is 11 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 260 flights scheduled in it.

Across the year

Alaska on SAN to BOS through the year

Darker means more delays. Figures are on-time percentages.May best, October worst

May is the best month on the calendar at 92.0% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. July was the busiest month here, with 61 flights.

Across the week, Monday is the strongest day at 82.7% on time and Friday the weakest at 74.7%, a spread of 8 points.

Arrival by arrival

How late Alaska on SAN to BOS runs when it is late

Alaska on SAN to BOS often beats the schedule: 163 of 494 completed flights, 33%, arrived 15 minutes or more early. The 107 late arrivals split 30 under half an hour, 35 between 30 and 60 minutes, and 42 an hour or more.

15+ min early163 flights33.0%
Within 15 min224 flights45.3%
15–29 min late30 flights6.1%
30–59 min late35 flights7.1%
1–2 hours late27 flights5.5%
2+ hours late15 flights3.0%

Scale runs 0% to 100%.

Share of 494 completed flights by arrival against schedule.

A late pushback is often recovered here: of 130 departures that left 15 minutes late or more, 46 still arrived on time. 23 flights left on time and still arrived late.

The worst days

Worst days for Alaska on SAN to BOS

The latest arrival of the period was on 31 December 2025, 6 hours 3 minutes behind schedule; most of its delay minutes were filed as extreme weather. The five worst days are spread across December, August, September and October, with no single month standing out.

The latest arrivals of Alaska on SAN to BOS in the period
Date	Arrived late by	Largest filed cause
31 December 2025	6 hours 3 minutes	Extreme weather
17 August 2026	6 hours	Carrier
18 September 2025	5 hours 21 minutes	Late-arriving aircraft
25 September 2025	4 hours 59 minutes	National Airspace System
13 October 2025	4 hours 33 minutes	Late-arriving aircraft

Delay causes

Why Alaska runs late on this route

National Airspace System accounts for 42% of the 7,670 delay minutes carriers reported here, and the remaining four split what is left.

National Airspace System
42%
Late-arriving aircraft
25%
Extreme weather
21%
Carrier
11%

Extreme weather accounts for 21% 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 3.6 times the usual weather exposure. The split is drawn from 7,670 reported delay minutes.

42% 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 3,233 minutes out of 7,670, against a national NAS share of 21%.

Cancellations sit at 1.38% against a national 1.89%, which is ordinary. Diversions add another 1.57%.

Connections and stage length

What a delay here costs

8.5% 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 a little over 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 74.6% on time across 508 flights, 4 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 4 points of difference.

One caution: this is a thin sample. 509 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. 509 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 78.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 494 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures