Flight profile · Alaska Airlines
AS306
Seattle (SEA) to Boston (BOS) · scheduled 6:30 AM – 4:45 PM
How AS306 performs
1,114 operations, July 2023 – July 2026.
AS306 arrived on time 77.6% of the time, against 75.2% for all SEA → BOS flights, so this departure is 2.4 percentage points better than the route as a whole. Against Alaska Airlines’ own flights on this route it is 4.7 points better.
Source: US DOT Bureau of Transportation Statistics · 1,114 operations, July 2023 – July 2026 · If AS306 is cancelled or significantly changed, DOT’s automatic refund rule may entitle you to your money back. The refund checker walks through eligibility.
Where AS306 is right now
A live reading, only if you ask for it. It is not part of the reliability record above.
Ask for the position of AS306 right now, if receivers on the ground are hearing it. Nothing is requested until you press the button.
Against the rest of the route
| Flight or route | On time | Cancelled | Median delay | Severe | Flights |
|---|---|---|---|---|---|
| AS306 | 77.6% | 1.26% | -4 min | 5.1% | 1,114 |
| Alaska Airlines on SEA → BOS | 72.9% | 0.75% | -2 min | 6.8% | 3,714 |
| All SEA → BOS flights | 75.2% | 0.94% | -4 min | 7.6% | 7,902 |
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
Why AS306 runs late
Where US DOT attributed the delay minutes on this flight.
airspace and airport capacity, including weather-driven flow control
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
the inbound aircraft was late, so this flight started late
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for AS306 on SEA → BOS. Only delays of 15 minutes or more are attributed.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
Does a late aircraft delay this flight?
How often the plane that flies AS306 comes in late, and what that does to the departure.
AS306 is usually the aircraft’s first flight of the day: the schedule gives it a median of 7.3 hours on the ground at SEA, so its “inbound” is mostly the aircraft’s arrival the evening before.
When the aircraft came in 15 or more minutes late, AS306 pushed back an average of 9 minutes late; when it came in on time or early, an average of 5 minutes late.
Each departure is matched to the flight the same aircraft flew into SEA just before it, using the tail number in the DOT file, 932 of 1,100 departures in all. A departure is left out when that flight is unknown, was cancelled or diverted, or the aircraft had sat for more than 12 hours. A flight the airline cancelled never left and is not in the count, and one flown by a substitute aircraft is matched to the aircraft that flew it, not to the one first planned.
Against the network at the same turn length
| Share of departures | Inbound landed 15+ late | Left 15+ late after a late inbound | Left 15+ late after an on-time inbound |
|---|---|---|---|
| AS306 | 23% | 19% | 15% |
| Network, same turn | 29% | 12% | 9% |
A night on the ground absorbs most of a late arrival, so a late inbound matters far less on a turn this long than on a same-day one.
The network row is every flight with a scheduled turn of 6 hours or more, usually overnight. How often AS306’s aircraft landed 15 or more minutes late is lower than the network’s and, once the aircraft was late, how often AS306 left 15 or more minutes late is higher than the network’s.
More: Which Flight Numbers Pay for a Late Aircraft lists the flight numbers that pass a late aircraft on.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
From pushback to gate
When it leaves SEA late, does that still matter by the time it reaches BOS?
AS306 pushes back an average of 7.7 minutes late and reaches the gate at BOS an average of 2.9 minutes late. The 4.7 minutes between those two figures are slack the published schedule already carries, which is why a late pushback on this flight does not reliably become a late arrival. It spends 23.2 minutes on the taxiways at SEA, 4.2 minutes longer than a typical SEA departure in the same hour.
On arrival at BOS, AS306 spends 11.1 min taxiing from touchdown to the gate — ground time a connecting passenger sits through before they can even leave the aircraft, on top of however late the flight itself ran. That is 2.1 minutes longer than a typical BOS arrival (9.0 min).
Departure delay is averaged over every pushback and arrival delay over every completed arrival, so the two counts differ by the flights that never reached BOS. Taxi-out is gate to wheels up and sits inside the scheduled block rather than on top of it; the comparison is 21,263 departures from SEA scheduled in the clock hour AS306 most often leaves in. Taxi-in is landing to gate, compared against every arrival FlyerIntel has on file at BOS (440,886 flights), not just AS306’s own. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
The hour it leaves SEA
Part of any flight’s record belongs to the clock rather than to the flight. AS306 has one departure time, so this is what that time is worth.
On-time arrival rate. 21,263 departures from SEA are scheduled in the 6 AM–7 AM hour over the period, against 510,205 across the whole day.
AS306 is scheduled out of SEA at 6:30 AM, in the 6 AM–7 AM bank. Departures from SEA in that hour arrive on time 91.2% of the time against 79.1% across the airport’s whole day — the slot alone is worth 12.1 points better before anything about this particular flight is considered.
The two airport figures cover every departure from SEA to every destination, so they describe the slot rather than this journey — the like-for-like comparison against the route is above. Hours are scheduled local, and a number whose schedule moved between banks inside the period has no single hour and is not described here at all. Why the hour matters.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Hours below 120 departures are not scored.
By day of week
Does AS306 run worse on particular days?
Monday is historically the most reliable day and Saturday the least, a gap of 7.7 percentage points.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Days with fewer than 120 operations are not scored.
Other routes AS306 has flown
A flight number is a slot in a schedule, and carriers reassign it. These are the other city pairs this number served in the analysis period.
| Route | Operated | Flights | On time |
|---|---|---|---|
| BOS→SEA Boston to Seattle | October 26, 2025 – June 9, 2026 | 116 | 58.4% |
Because the same number has served different journeys, the statistics above describe only the route AS306 currently operates. Blending them would produce an average of two different flights.
When it goes wrong
The average describes a usual day. This is the day that ruins a connection.
33 min late
against a median of 4 min early
Percentiles over 1,114 operations; cancelled and diverted flights are counted separately.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
Other flights on this route
Same airports, same journey, different odds of arriving on time.
| Flight | Airline | On time | Median arrival | Operations |
|---|---|---|---|---|
| DL459 | Delta Air Lines | 89.4% | 14 min early | 785 |
| DL473 | Delta Air Lines | 84.0% | 8 min early | 782 |
| AS306 this flight | Alaska Airlines | 77.6% | 4 min early | 1,114 |
| AS460 | Alaska Airlines | 75.0% | 3 min early | 1,065 |
| AS536 | Alaska Airlines | 72.7% | 1 min early | 811 |
Every departure listed carries at least 600 operations, so the comparison is between figures that mean something. AS306 is placed in the same ordering rather than left out of it; the rows around it are the most punctual departures on the route, not all of them, so this is a comparison and not a rank. Schedules change; confirm the departure still operates before booking around this.
Data and methodology
Calculated by FlyerIntel from 1,114 records of AS306 operating SEA → BOS, published by the US DOT Bureau of Transportation Statistics. A flight counts as delayed when it arrives 15 or more minutes after schedule. Cancelled and diverted flights are excluded from the on-time rate and reported separately. Flight numbers are resolved as carrier plus number plus route, because the same number serves different routes over time.
Full methodology · Data sources · Report a problem
Related research: Most and Least Reliable Flight Numbers · The Delay You Inherit · Making Up Time in the Air
Analysis last recomputed