Flight number record
AS 528
Alaska Airlines · Seattle to San Francisco
- Route
- SEA → SFO
- Departs
- 08:53
- Flights
- 250
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s AS 528, check with Alaska Airlines.
AS 528 earns an F, which is as low as this site's scale goes for a reason. Only 50.2% of flights arrive inside the 15-minute window, 27 points worse than the national rate of 77.3%. Late arrivals average roughly 50 minutes. Treat any tight connection here as a coin flip. That rests on 250 flights, with a median arrival 14 minutes late.
The national on-time rate over the same period is 77.3%, so AS 528 runs 27 points behind the country as a whole. Across a thousand flights that is about 271 extra late arrivals.
Key figures
On time
50.2%
Arrivals under 15 minutes late, of 247 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
1.20%
National rate is 1.89%
1 hour+ late
13.4%
National rate is 8.3%
These figures cover 250 flights between September 2025 and August 2026. Beyond the headline rate, 13.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When AS 528 flies
AS 528 flies SEA to SFO without a single fixed slot. Its most common scheduled departure was 08:53, used on 69 of 250 flights, with 20:50 (36 flights) next.
- Departs 08:5369 flights27.6%
- Departs 20:5036 flights14.4%
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 08:53 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and AS 528 runs 34 points worse at 50.2%. 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 528 next to SEA to SFO
Every carrier on SEA to SFO combined arrived on time 59.8% of the time across 6,817 flights, so AS 528 is 10 points behind it. Alaska flew 2,727 flights on the same city pair under all its flight numbers, including this one, and those ran 56.0% on time. Across its whole network Alaska Airlines managed 79.7%, which this flight trails by 30 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| AS 528thin sample | 250 | 50.2% | 52 min | 1.20% | F |
| All Alaska Airlines on SEA–SFO | 2,727 | 56.0% | 52 min | 1.14% | D |
| All carriers on SEA–SFO | 6,817 | 59.8% | 57 min | 1.11% | D |
| Alaska Airlines, whole network | 309,844 | 79.7% | 52 min | 1.20% | B |
Across the year
AS 528 quarter by quarter
AS 528 did not run the same all year. Its best quarter was Jan–Mar 2026 at 76.2% on time and its weakest Apr–Jun 2026 at 29.4%, a swing of 47 points on roughly 63 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.
- Oct–Dec 202555 flights63.6%
- Jan–Mar 202665 flights76.2%
- Apr–Jun 202668 flights29.4%
- Jul–Sep 202662 flights34.4%
Scale runs 20% to 80%.
By weekday, AS 528 did best on Friday at 62.2% on time and worst on Sunday at 43.6%. Each day rests on about 36 flights, so a gap of 19 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late AS 528 runs when it is late
The 123 late arrivals split 39 under half an hour, 51 between 30 and 60 minutes, and 33 an hour or more.
- 15+ min early34 flights13.8%
- Within 15 min90 flights36.4%
- 15–29 min late39 flights15.8%
- 30–59 min late51 flights20.6%
- 1–2 hours late25 flights10.1%
- 2+ hours late8 flights3.2%
Scale runs 0% to 100%.
Share of 247 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 110 departures that left 15 minutes late or more, only 12 made it up before arrival. In the other direction, 25 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 SFO.
The worst days
Worst days for AS 528
The latest arrival of the period was on 5 January 2026, 3 hours 22 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across January, February, May and June, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 5 January 2026 | 3 hours 22 minutes | Carrier |
| 15 February 2026 | 2 hours 55 minutes | National Airspace System |
| 14 May 2026 | 2 hours 48 minutes | Late-arriving aircraft |
| 12 February 2026 | 2 hours 46 minutes | Carrier |
| 8 June 2026 | 2 hours 37 minutes | National Airspace System |
Delay causes
Why AS 528 runs late
National Airspace System accounts for 71% of the 6,378 delay minutes carriers reported here, and the remaining four split what is left.
- 71%National Airspace System
- 15%Late-arriving aircraft
- 12%Carrier
- 1%Extreme weather
71% 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 4,552 minutes out of 6,378, against a national NAS share of 21%. The split is drawn from 6,378 delay minutes reported on AS 528.
Cancellations sit at 1.20% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
13.4% 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.
The 679 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
Every one of the 250 flights under AS 528 in the data flew SEA to SFO. 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. 250 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 528
For a booking, AS 528 is a flight to put a long connection behind. 13.4% of its completed flights arrived an hour or more late, which a short layover will not absorb. If the onward flight is on a separate ticket, the risk sits with you.
Related
Where to go next
- SEA to SFO, every carrier and departure
- SFO to SEA, the return direction
- United Airlines 737 on the same route53.9%
- Delta Air Lines 1412 on the same route60.1%
- Delta Air Lines 2635 on the same route69.6%
- SkyWest Airlines 3707 on the same route68.5%
- Alaska Airlines 655 on the same route67.2%
- Alaska Airlines 725 on the same route50.5%
- Seattle-Tacoma International (SEA) delay statistics
- San Francisco International (SFO) 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
- The best time of day to fly, according to 7.05 million flight records
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.