Flight number record
AS 390
Alaska Airlines · San Diego to Boston
- Route
- SAN → BOS
- Departs
- 07:00
- Flights
- 358
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s AS 390, check with Alaska Airlines.
AS 390 lands a B, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 358 flights, with a median arrival 3 minutes early.
Key figures
On time
76.5%
Arrivals under 15 minutes late, of 345 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
1.40%
National rate is 1.89%
1 hour+ late
9.0%
National rate is 8.3%
These figures cover 358 flights between September 2025 and August 2026. Beyond the headline rate, 9.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When AS 390 flies
AS 390 flies SAN to BOS without a single fixed slot. Its most common scheduled departure was 07:00, used on 98 of 358 flights, with 08:50 (67 flights) and 08:00 (42 flights) next.
- Departs 07:0098 flights27.4%
- Departs 08:5067 flights18.7%
- Departs 08:0042 flights11.7%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 07:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and AS 390 runs 13 points worse at 76.5%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
AS 390 next to SAN to BOS
Every carrier on SAN to BOS combined arrived on time 75.5% of the time across 1,881 flights, so AS 390 is about level with it. Across its whole network Alaska Airlines managed 79.7%, which this flight trails by 3 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| AS 390thin sample | 358 | 76.5% | 77 min | 1.40% | B |
| All Alaska Airlines on SAN–BOS | 509 | 78.3% | 72 min | 1.38% | B |
| All carriers on SAN–BOS | 1,881 | 75.5% | 84 min | 1.70% | B |
| Alaska Airlines, whole network | 309,844 | 79.7% | 52 min | 1.20% | B |
Across the year
AS 390 quarter by quarter
AS 390 did not run the same all year. Its best quarter was Apr–Jun 2026 at 91.1% on time and its weakest Oct–Dec 2025 at 65.5%, a swing of 26 points on roughly 90 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202530 flights—
- Oct–Dec 202590 flights65.5%
- Jan–Mar 202685 flights78.5%
- Apr–Jun 202691 flights91.1%
- Jul–Sep 202662 flights75.0%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
By weekday, AS 390 did best on Saturday at 88.9% on time and worst on Sunday at 70.0%. Each day rests on about 51 flights, so a gap of 19 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late AS 390 runs when it is late
AS 390 often beats the schedule: 106 of 345 completed flights, 31%, arrived 15 minutes or more early. The 81 late arrivals split 22 under half an hour, 28 between 30 and 60 minutes, and 31 an hour or more.
- 15+ min early106 flights30.7%
- Within 15 min158 flights45.8%
- 15–29 min late22 flights6.4%
- 30–59 min late28 flights8.1%
- 1–2 hours late17 flights4.9%
- 2+ hours late14 flights4.1%
Scale runs 0% to 100%.
Share of 345 completed flights by arrival against schedule.
17 of 77 late departures made up the time and arrived on time, 22% of them. In the other direction, 21 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 BOS.
The worst days
Worst days for AS 390
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.
| 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 AS 390 runs late
National Airspace System accounts for 51% of the 6,235 delay minutes carriers reported here, and the remaining four split what is left.
- 51%National Airspace System
- 24%Extreme weather
- 19%Late-arriving aircraft
- 7%Carrier
Extreme weather accounts for 24% 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 quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 3.9 times the usual weather exposure. The split is drawn from 6,235 delay minutes reported on AS 390.
Cancellations sit at 1.40% against a national 1.89%, which is ordinary. Diversions add another 2.23%.
Connections and routes
What a delay on this flight costs
9.0% 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.
Every one of the 358 flights under AS 390 in the data flew SAN to BOS. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 358 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 AS 390
For a booking, read AS 390 as 76.5% on time with 1.40% cancelled over 358 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- SAN to BOS, every carrier and departure
- BOS to SAN, the return direction
- JetBlue Airways 2120 on the same route81.7%
- JetBlue Airways 620 on the same route75.5%
- San Diego International (SAN) delay statistics
- Boston Logan International (BOS) delay statistics
- Alaska Airlines on-time record
- Every Alaska Airlines flight number with a record
- The most and least reliable flight numbers in the US
- How often a connection fails at the major US hubs
A flight number here means Alaska Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
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.