Route reliability record
SAN→BOS
San Diego to Boston
- Flights
- 1,881
- Period
- September 2025 to August 2026
- Distance
- 2,588 mi
- Carriers
- 4
This route sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.3%. The late ones land an hour and a half behind schedule. That rests on 1,881 SAN to BOS flights, of which Alaska Airlines flew 509 at 78.3% on time.
Best time to fly SAN to BOS: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 84.5% of the time and Saturday flights 81.5%, against 75.5% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
75.5%
Arrivals under 15 minutes late, of 1,837 completed flights
Avg delay
84 min
Across delayed arrivals only, not all flights
Cancelled
1.70%
National rate is 1.89%
Best carrier
Alaska
78.3% on time across 509 flights
These figures cover 1,881 flights between September 2025 and August 2026. Beyond the headline rate, 10.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on SAN to BOS
The two carriers here are closely matched: 2 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 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+ |
No carrier stands out. Alaska tops the table at 78.3%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on SAN to BOS
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly San Diego to Boston
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SAN → BOSSan Diego to Boston | Alaska Airlines | 77.2% | 78.3% | 1.38% | 5am–8am, Mon | AS 390 07:00 |
| 2. SAN → BOSSan Diego to Boston | JetBlue Airways | 75.0% | 76.6% | 2.07% | 8pm–5am, Sat | B6 2120 20:40 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against 2 points between the best and worst carrier.
- 5am–8am98 flights84.5%
- 8am–11am330 flights71.7%
- 11am–2pm331 flights73.4%
- 2pm–5pm244 flights61.5%
- 5pm–8pm—
- 8pm–5am878 flights80.5%
Scale runs 55% 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 61.5% for the afternoon 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 8pm–5am window is the busiest, with 878 flights scheduled in it.
Explore
Filter SAN to BOS by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On SAN to BOS, the best departure window is 5am–8am at 84.5% on time and the worst is 2pm–5pm at 61.5%, a wide gap of 23.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am84.5%
- 8–11am71.7%
- 11am–2pm73.4%
- 2–5pm61.5%
- 5–8pm—
- 8pm–5am80.5%
best all US flightsScale 55% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 26 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 64.2% on time, 26 points below May, the best at 90.2%. 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 212 flights.
Across the week, Saturday is the strongest day at 81.5% on time and Thursday the weakest at 70.2%, a spread of 11 points.
Delay causes
Why this route gets delayed
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 38,000 reported delay minutes.
- 36%Late-arriving aircraft
- 30%National Airspace System
- 26%Carrier
- 8%Extreme weather
- 0%Security
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 38,000 reported delay minutes here, that single category outweighs weather by 4 to one. The split is drawn from 37,993 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 84.5% on time here.
Cancellations sit at 1.70% against a national 1.89%, which is ordinary. Diversions add another 0.64%.
Connections and stage length
What a delay here actually costs
10.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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 runs 75.3% on time across 1,880 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,881 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in BOS after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 90.2% on time and July 64.2%, a swing of 26 points. If the dates move at all, move them out of July before you think about anything else. 1,837 completed flights over 12 months sit behind that.
Common questions
SAN to BOS questions
How often is SAN to BOS delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.5% of the 1,881 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on SAN to BOS?
Alaska Airlines leads at 78.3% on time across 509 flights. JetBlue Airways is at the other end on 76.6%, a gap of 2 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on SAN to BOS?
The 5am–8am departure window is the strongest at 84.5% on time. The 2pm–5pm window is the weakest at 61.5%, 23 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on SAN to BOS?
July is the weakest month at 64.2% on time, compared with 90.2% in May. Across the year that is 26 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- BOS to SAN — the return legseparate record
- San Diego International (SAN) delay statistics
- Boston Logan International (BOS) delay statistics
- Alaska Airlines on SAN to BOS78.3%
- Delta Air Lines on SAN to BOS78.2%
- JetBlue Airways on SAN to BOS76.6%
- SAN to SFO, a related route59.5%
- DCA to BOS, a related route70.1%
- SAN to DEN, a related route78.4%
- Alaska Airlines on-time record78.3%
- Delta Air Lines on-time record78.2%
- JetBlue Airways on-time record76.6%
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
Direction matters. SAN to BOS and BOS to SAN are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.