Route reliability record
PHX→SEA
Phoenix to Seattle
- Flights
- 7,269
- Period
- July 2025 to June 2026
- Distance
- 1,107 mi
- Carriers
- 7
This route lands a B+, 5 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by about 55 minutes on average. That is a workable record, not a spotless one. That rests on 7,269 flights, of which Delta Air Lines flew 1,764 at 87.8% on time.
Delta Air Lines is the most reliable of the five carriers covered here at 87.8% on time across 1,764 flights.
Key figures
On time
82.7%
Arrivals under 15 minutes late, of 7,211 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.65%
National rate is 1.81%
Best carrier
Delta
87.8% on time across 1,764 flights
These figures cover 7,269 flights between July 2025 and June 2026. The median arrival is 7 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.
Carrier by carrier
Which airline is most reliable on PHX to SEA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 87.8% of the time; Southwest Airlines manages 64.8%. Sample sizes sit next to every figure, because a two-point gap across 1,037 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,764 | 87.8% | 73 min | 0.85% | A+ |
| Envoy Air | 692 | 87.1% | 45 min | 0.00% | A+ |
| Frontier Airlinesthin sample | 165 | 86.1% | 80 min | 0.00% | A+ |
| Alaska Airlines | 2,903 | 84.9% | 56 min | 0.76% | B+ |
| SkyWest Airlines | 506 | 82.6% | 61 min | 0.59% | B+ |
| American Airlinesthin sample | 202 | 81.6% | 53 min | 0.50% | B+ |
| Southwest Airlines | 1,037 | 64.8% | 43 min | 0.58% | D+ |
The spread between Delta and Southwest is 23 points, wide enough that it should decide the booking. On a hundred trips that is 23 more arrivals inside the on-time window.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 20 points, against 23 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,323 flights90.5%
- 8am–11am1,219 flights81.9%
- 11am–2pm1,428 flights86.6%
- 2pm–5pm1,509 flights80.8%
- 5pm–8pm1,286 flights77.9%
- 8pm–5am504 flights70.9%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.5% of the time, against 70.9% for the overnight window. That is 20 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 1,509 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 13 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 77.2% on time, against 90.3% in February. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. March was the busiest month here, with 685 flights.
Across the week, Tuesday is the strongest day at 85.8% on time and Friday the weakest at 79.5%. 6 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 47% of the 69,000 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.
- 47%Late-arriving aircraft
- 34%Carrier
- 16%National Airspace System
- 4%Extreme weather
- 0%Security
47% 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 69,000 reported delay minutes here, that single category outweighs weather by 12 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 68,520 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.5% on time here.
Cancellations are rare at 0.65%, 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 stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.2% 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.
The return leg is a different operation and performs like one: it runs 79.2% on time across 7,268 flights, 4 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 4 points of difference.
The sample behind these figures is 7,269 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 90.3% on time and December 77.2%, a swing of 13 points. If the dates move at all, move them out of December before you think about anything else. 7,211 completed flights over 12 months sit behind that.
Common questions
PHX to SEA questions
How often is PHX to SEA delayed?
About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.3% of the 7,269 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 55 minutes on average.
Which airline is most reliable on PHX to SEA?
Delta Air Lines leads at 87.8% on time across 1,764 flights. Southwest Airlines is at the other end on 64.8%, a gap of 23 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on PHX to SEA?
The 5am–8am departure window is the strongest at 90.5% on time. The 8pm–5am window is the weakest at 70.9%, 20 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on PHX to SEA?
December is the weakest month at 77.2% on time, compared with 90.3% in February. Across the year that is 13 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SEA to PHX — the return legseparate record
- Phoenix Sky Harbor International (PHX) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on-time record87.8%
- Envoy Air on-time record87.1%
- Frontier Airlines on-time record86.1%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. PHX to SEA and SEA to PHX are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.