Flight number record
AS 603
Alaska Airlines · Phoenix to Seattle
- Route
- PHX → SEA
- Departs
- 11:52
- Flights
- 346
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 2026, not live status. For today’s AS 603, check with Alaska Airlines.
AS 603 earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 11 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 346 flights, with a median arrival 12 minutes early.
Set against the rest of the country, AS 603's record is 11 points better than the US average of 77.6%. That gap is worth roughly 111 fewer late arrivals for every thousand flights.
Key figures
On time
88.7%
Arrivals under 15 minutes late, of 344 completed flights
Avg delay
89 min
Across delayed arrivals only, not all flights
Cancelled
0.58%
National rate is 1.81%
1 hour+ late
3.5%
National rate is 8.1%
These figures cover 346 flights between July 2025 and June 2026. The median arrival is 12 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Schedule
When AS 603 flies
AS 603 flies PHX to SEA without a single fixed slot. Its most common scheduled departure was 11:52, used on 50 of 346 flights, with 12:00 (42 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 11:5250 flights14.5%
- Departs 12:0042 flights12.1%
Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 11:52 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.8%, and AS 603 runs 10 points better at 88.7%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
Against the route
AS 603 next to PHX to SEA
Every carrier on PHX to SEA combined arrived on time 82.7% of the time across 7,269 flights, so AS 603 is 6 points ahead of it. Alaska flew 2,903 flights on the same city pair under all its flight numbers, including this one, and those ran 84.9% on time. Across its whole network Alaska Airlines managed 79.1%, which this flight beats by 10 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| AS 603thin sample | 346 | 88.7% | 89 min | 0.58% | A+ |
| All Alaska Airlines on PHX–SEA | 2,903 | 84.9% | 56 min | 0.76% | B+ |
| All carriers on PHX–SEA | 7,269 | 82.7% | 55 min | 0.65% | B+ |
| Alaska Airlines, whole network | 293,372 | 79.1% | 52 min | 1.28% | B |
Across the year
AS 603 quarter by quarter
AS 603 did not run the same all year. Its best quarter was Apr–Jun 2026 at 92.7% on time and its weakest Jan–Mar 2026 at 81.9%, a swing of 11 points on roughly 87 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 202590 flights92.2%
- Oct–Dec 202589 flights87.6%
- Jan–Mar 202683 flights81.9%
- Apr–Jun 202684 flights92.7%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, AS 603 did best on Wednesday at 94.2% on time and worst on Friday at 81.6%. Each day rests on about 49 flights, so a gap of 13 points is worth noticing but could still narrow in another year.
Delay causes
Why AS 603 runs late
One category carries most of the weight here. Late-arriving aircraft accounts for 73% of the 3,455 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 73%Late-arriving aircraft
- 19%Carrier
- 9%National Airspace System
- 0%Extreme weather
73% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 3,455 reported delay minutes here, that single category outweighs weather by 73 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 3,455 delay minutes reported on AS 603.
Cancellations are rare at 0.58%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 3.5% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 1,107 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
Every one of the 346 flights under AS 603 in the data flew PHX to SEA. 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. 346 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 603
For a booking, AS 603 has one of the better records a US domestic flight can show: 88.7% on time and 0.58% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- PHX to SEA, every carrier and departure
- SEA to PHX, the return direction
- Delta Air Lines 2419 on the same route92.8%
- Alaska Airlines 637 on the same route87.6%
- Delta Air Lines 2444 on the same route95.2%
- Alaska Airlines 645 on the same route84.2%
- Alaska Airlines 611 on the same route79.8%
- Phoenix Sky Harbor International (PHX) delay statistics
- Seattle-Tacoma International (SEA) 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
- Why the first flight of the morning is statistically safest
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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.