Flight profile · Alaska Airlines
AS21
New York (JFK) to Seattle (SEA) · scheduled 9:30 AM – 10:16 AM
How AS21 performs
968 operations, July 2023 – July 2026.
AS21’s scheduled departure has moved during the period FlyerIntel has on file: it typically left around 9:30 AM earlier on, and around 7:00 AM more recently — a 150-minute shift, not the few minutes of day-to-day rounding every published schedule carries. Confirm the current departure time before booking around an older listing.
Source: US DOT Bureau of Transportation Statistics · 968 operations, July 2023 – July 2026 · If AS21 is cancelled or significantly changed, DOT’s automatic refund rule may entitle you to your money back. The refund checker walks through eligibility.
Where AS21 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 AS21 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 |
|---|---|---|---|---|---|
| AS21 | 76.6% | 2.17% | -7 min | 6.6% | 968 |
| Alaska Airlines on JFK → SEA | 76.8% | 2.20% | -7 min | 7.3% | 4,223 |
| All JFK → SEA flights | 76.4% | 1.93% | -7 min | 7.6% | 9,123 |
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
Why AS21 runs late
Where US DOT attributed the delay minutes on this flight.
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow control
the inbound aircraft was late, so this flight started late
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for AS21 on JFK → SEA. 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 AS21 comes in late, and what that does to the departure.
When the aircraft came in 15 or more minutes late, AS21 pushed back an average of 20 minutes late; when it came in on time or early, an average of 1 minute late.
Each departure is matched to the flight the same aircraft flew into JFK just before it, using the tail number in the DOT file, 901 of 952 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 |
|---|---|---|---|
| AS21 | 28% | 31% | 8% |
| Network, same turn | 23% | 40% | 9% |
The schedule leaves a long gap on the ground, which gives a late aircraft room to catch up before this flight pushes back.
The network row is every flight with a scheduled turn of 90 minutes to 3 hours. How often AS21’s aircraft landed 15 or more minutes late is higher than the network’s and, once the aircraft was late, how often AS21 left 15 or more minutes late is lower 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 JFK late, does that still matter by the time it reaches SEA?
AS21 pushes back an average of 7.9 minutes late and reaches the gate at SEA an average of 3.3 minutes late. The 4.6 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. Its 27.6 minutes on the taxiways at JFK is about what any departure from the airport in that hour spends.
On arrival at SEA, AS21 spends 12.1 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 about what any arrival at SEA spends on the ground before reaching the gate.
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 SEA. Taxi-out is gate to wheels up and sits inside the scheduled block rather than on top of it; the comparison is 25,535 departures from JFK scheduled in the clock hour AS21 most often leaves in. Taxi-in is landing to gate, compared against every arrival FlyerIntel has on file at SEA (510,187 flights), not just AS21’s own. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
The hour it leaves JFK
Part of any flight’s record belongs to the clock rather than to the flight. AS21 has one departure time, so this is what that time is worth.
On-time arrival rate. 25,535 departures from JFK are scheduled in the 9 AM–10 AM hour over the period, against 351,635 across the whole day.
AS21 is scheduled out of JFK at 9:30 AM, in the 9 AM–10 AM bank. Departures from JFK in that hour arrive on time 81.7% of the time against 77.0% across the airport’s whole day — the slot alone is worth 4.6 points better before anything about this particular flight is considered.
The two airport figures cover every departure from JFK 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 AS21 run worse on particular days?
Tuesday is historically the most reliable day and Thursday the least, a gap of 12.0 percentage points.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Days with fewer than 120 operations are not scored.
When it goes wrong
The average describes a usual day. This is the day that ruins a connection.
37 min late
against a median of 7 min early
Percentiles over 968 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 |
|---|---|---|---|---|
| AS23 | Alaska Airlines | 85.0% | 12 min early | 1,006 |
| DL699 | Delta Air Lines | 81.2% | 9 min early | 814 |
| AS31 | Alaska Airlines | 80.6% | 7 min early | 1,111 |
| AS21 this flight | Alaska Airlines | 76.6% | 7 min early | 968 |
| DL740 | Delta Air Lines | 72.8% | 6 min early | 800 |
| DL688 | Delta Air Lines | 68.3% | 0 min early | 807 |
| B6263 | JetBlue | 65.3% | 1 min early | 674 |
| AS17 | Alaska Airlines | 65.2% | 0 min early | 1,048 |
Every departure listed carries at least 600 operations, so the comparison is between figures that mean something. AS21 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 968 records of AS21 operating JFK → SEA, 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