Flight number record
AS 603
Alaska Airlines · Phoenix to Seattle
- Route
- PHX → SEA
- Departs
- 11:23
- Flights
- 347
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 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 10 points better than the national rate of 77.3%. When something does go wrong the average delay runs an hour and a half. That rests on 347 flights, with a median arrival 11 minutes early.
Set against the rest of the country, AS 603's record is 10 points better than the US average of 77.3%. That gap is worth roughly 99 fewer late arrivals for every thousand flights.
Key figures
On time
87.2%
Arrivals under 15 minutes late, of 343 completed flights
Avg delay
91 min
Across delayed arrivals only, not all flights
Cancelled
1.15%
National rate is 1.89%
1 hour+ late
4.1%
National rate is 8.3%
These figures cover 347 flights between September 2025 and August 2026. The median arrival is 11 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.
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Schedule
When AS 603 flies
AS 603 flies PHX to SEA without a single fixed slot. Its most common scheduled departure was 11:23, used on 69 of 347 flights.
- Departs 11:2369 flights19.9%
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 11:23 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and AS 603 runs 9 points better at 87.2%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
AS 603 next to PHX to SEA
Every carrier on PHX to SEA combined arrived on time 82.2% of the time across 7,202 flights, so AS 603 is 5 points ahead of it. Alaska flew 2,886 flights on the same city pair under all its flight numbers, including this one, and those ran 84.4% on time. Across its whole network Alaska Airlines managed 79.7%, which this flight beats by 8 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| AS 603thin sample | 347 | 87.2% | 91 min | 1.15% | A |
| All Alaska Airlines on PHX–SEA | 2,886 | 84.4% | 56 min | 0.76% | B+ |
| All carriers on PHX–SEA | 7,202 | 82.2% | 56 min | 0.69% | B+ |
| Alaska Airlines, whole network | 309,844 | 79.7% | 52 min | 1.20% | 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 202529 flights—
- Oct–Dec 202589 flights87.6%
- Jan–Mar 202683 flights81.9%
- Apr–Jun 202684 flights92.7%
- Jul–Sep 202662 flights85.0%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, AS 603 did best on Wednesday at 96.2% on time and worst on Monday at 82.7%. Each day rests on about 50 flights, so a gap of 14 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late AS 603 runs when it is late
AS 603 often beats the schedule: 126 of 343 completed flights, 37%, arrived 15 minutes or more early. The 44 late arrivals split 17 under half an hour, 13 between 30 and 60 minutes, and 14 an hour or more.
- 15+ min early126 flights36.7%
- Within 15 min173 flights50.4%
- 15–29 min late17 flights5.0%
- 30–59 min late13 flights3.8%
- 1–2 hours late3 flights0.9%
- 2+ hours late11 flights3.2%
Scale runs 0% to 100%.
Share of 343 completed flights by arrival against schedule.
8 of 42 late departures made up the time and arrived on time, 19% of them. 10 flights left on time and still arrived late.
The worst days
Worst days for AS 603
The latest arrival of the period was on 26 January 2026, 9 hours 41 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 26 January 2026 | 9 hours 41 minutes | Late-arriving aircraft |
| 26 September 2025 | 7 hours 11 minutes | Late-arriving aircraft |
| 20 August 2026 | 5 hours 20 minutes | Late-arriving aircraft |
| 8 June 2026 | 4 hours 27 minutes | Late-arriving aircraft |
| 11 February 2026 | 4 hours 4 minutes | Late-arriving aircraft |
Delay causes
Why AS 603 runs late
Late-arriving aircraft accounts for 69% of the 4,017 delay minutes carriers reported here, and the remaining four split what is left.
- 69%Late-arriving aircraft
- 20%Carrier
- 11%National Airspace System
- 0%Extreme weather
69% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 4,017 reported delay minutes here, that single category outweighs weather by 69 to one. The split is drawn from 4,017 delay minutes reported on AS 603.
Cancellations sit at 1.15% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 4.1% land an hour or more behind schedule, against 8.3% 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.
Every one of the 347 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. 347 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: 87.2% on time and 1.15% 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 route84.0%
- Alaska Airlines 645 on the same route85.1%
- Alaska Airlines 611 on the same route81.5%
- Delta Air Lines 2444 on the same route94.2%
- 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.