Carrier route record

ASBOS→SAN

Alaska Airlines · Boston to San Diego

Flights: 508
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 BOS 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 a little over an hour behind schedule. That rests on 508 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 BOS to SAN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

74.6%

Arrivals under 15 minutes late, of 496 completed flights

Avg delay

71 min

Across delayed arrivals only, not all flights

Cancelled

1.57%

National rate is 1.89%

Whole route

75.3%

Every carrier on BOS to SAN, 1,880 flights

These figures cover 508 flights between September 2025 and August 2026. Beyond the headline rate, 8.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.

Fare search by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.

Carrier by carrier

Alaska against every carrier on BOS to SAN

Alaska flew 508 of the 1,880 flights on BOS to SAN, about 27% of it. Its 74.6% on time is about level with the route as a whole at 75.3%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from JetBlue at 82.4% to Southwest at 44.8%. 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 BOS to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
JetBlue Airways	919	82.4%	69 min	1.96%	B
Alaska Airlines (this page)	508	74.6%	71 min	1.57%	C
Delta Air Linesthin sample	364	66.0%	44 min	1.65%	C
Southwest Airlinesthin sample	89	44.8%	67 min	2.25%	F

Flight by flight

Alaska flight numbers on BOS to SAN

AS 38916:3369.5% · 314 flights

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

5am–8am52 flights67.3%
8am–11am132 flights87.6%
11am–2pm—
2pm–5pm167 flights74.8%
5pm–8pm157 flights65.8%
8pm–5am—

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 87.6% of the time, against 65.8% for the evening window. That is 22 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 167 flights scheduled in it.

Across the year

Alaska on BOS to SAN through the year

Darker means more delays. Figures are on-time percentages.July best, June worst

June is the worst month at 66.7% on time, 19 points below July, the best at 85.2%. 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 78.7% on time and Friday the weakest at 71.1%, a spread of 8 points.

Arrival by arrival

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

Alaska on BOS to SAN often beats the schedule: 170 of 496 completed flights, 34%, arrived 15 minutes or more early. The 126 late arrivals split 47 under half an hour, 38 between 30 and 60 minutes, and 41 an hour or more.

15+ min early170 flights34.3%
Within 15 min200 flights40.3%
15–29 min late47 flights9.5%
30–59 min late38 flights7.7%
1–2 hours late27 flights5.4%
2+ hours late14 flights2.8%

Scale runs 0% to 100%.

Share of 496 completed flights by arrival against schedule.

30 of 101 late departures made up the time and arrived on time, 30% of them. In the other direction, 55 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SAN.

The worst days

Worst days for Alaska on BOS to SAN

The latest arrival of the period was on 16 July 2026, 15 hours 13 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.

The latest arrivals of Alaska on BOS to SAN in the period
Date	Arrived late by	Largest filed cause
16 July 2026	15 hours 13 minutes	Carrier
28 December 2025	9 hours 45 minutes	Carrier
13 October 2025	6 hours 52 minutes	Late-arriving aircraft
22 July 2026	6 hours 43 minutes	Carrier
13 March 2026	5 hours 47 minutes	Late-arriving aircraft

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 8,890 reported delay minutes.

Carrier
38%
National Airspace System
30%
Late-arriving aircraft
28%
Extreme weather
4%

The largest share of delay minutes, 38%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,366 of the 8,890 delay minutes reported here. The split is drawn from 8,890 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 87.6% on time here.

Cancellations sit at 1.57% against a national 1.89%, 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 8.3%, 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 78.3% on time across 509 flights, 4 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 4 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 74.6% 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.

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