Route reliability record
PDX→SEA
Portland to Seattle
- Flights
- 4,927
- Period
- September 2025 to August 2026
- Distance
- 129 mi
- Carriers
- 3
This route earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs about 55 minutes. That rests on 4,927 PDX to SEA flights, of which SkyWest Airlines flew 3,472 at 85.5% on time.
Best time to fly PDX to SEA: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 90.7% of the time and Tuesday flights 87.8%, against 84.9% for the route overall.
Set against the rest of the country, this route's record is 8 points better than the US average of 77.3%. That gap is worth roughly 76 fewer late arrivals for every thousand flights.
Key figures
On time
84.9%
Arrivals under 15 minutes late, of 4,892 completed flights
Avg delay
54 min
Across delayed arrivals only, not all flights
Cancelled
0.71%
National rate is 1.89%
Best carrier
SkyWest
85.5% on time across 3,472 flights
These figures cover 4,927 flights between September 2025 and August 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.
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Carrier by carrier
Which airline is most reliable on PDX to SEA
The two carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Linesthin sample | 250 | 89.6% | 68 min | 0.00% | A+ |
| SkyWest Airlines | 3,472 | 85.5% | 59 min | 0.58% | A+ |
| Alaska Airlines | 1,205 | 82.1% | 42 min | 1.24% | B |
No carrier stands out. SkyWest tops the table at 85.5%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on PDX to SEA
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Portland to Seattle
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. PDX → SEAPortland to Seattle | SkyWest Airlines | 85.0% | 85.5% | 0.58% | 5am–8am, Tue | OO 3818 11:10 |
| 2. PDX → SEAPortland to Seattle | Alaska Airlines | 81.1% | 82.1% | 1.24% | 5am–8am, Sun | AS 499 06:00 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 10 points, against 3 points between the best and worst carrier.
- 5am–8am1,242 flights90.7%
- 8am–11am955 flights80.6%
- 11am–2pm902 flights85.7%
- 2pm–5pm720 flights84.4%
- 5pm–8pm794 flights81.4%
- 8pm–5am314 flights82.4%
Scale runs 70% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.7% of the time, against 80.6% for the morning window. That is 10 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 1,242 flights scheduled in it.
Explore
Filter PDX to SEA by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On PDX to SEA, the best departure window is 5am–8am at 90.7% on time and the worst is 8am–11am at 80.6%, a wide gap of 10.1 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am90.7%
- 8–11am80.6%
- 11am–2pm85.7%
- 2–5pm84.4%
- 5–8pm81.4%
- 8pm–5am82.4%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 17 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.
August is the worst month at 74.6% on time, 17 points below February, the best at 91.2%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. September was the busiest month here, with 463 flights.
Across the week, Tuesday is the strongest day at 87.8% on time and Thursday the weakest at 80.4%, a spread of 7 points.
Delay causes
Why this route gets delayed
Carrier accounts for 45% of the 40,000 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Carrier
- 23%National Airspace System
- 18%Late-arriving aircraft
- 14%Extreme weather
- 0%Security
Extreme weather accounts for 14% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.3 times the usual weather exposure. The split is drawn from 40,123 reported delay minutes.
The largest share of delay minutes, 45%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 18,000 of the 40,000 delay minutes reported here.
Cancellations are rare at 0.71%, below the national 1.89% 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 3.7% 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.
At 129 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg runs 82.2% on time across 4,826 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 4,927 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.
Work out the risk of missing a connection in SEA after this flight
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 91.2% on time and August 74.6%, a swing of 17 points. If the dates move at all, move them out of August before you think about anything else. 4,892 completed flights over 12 months sit behind that.
Common questions
PDX to SEA questions
How often is PDX to SEA delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 15.1% of the 4,927 flights in this analysis, against 22.7% nationally. Delayed flights are late by about 55 minutes on average.
Which airline is most reliable on PDX to SEA?
SkyWest Airlines leads at 85.5% on time across 3,472 flights. Alaska Airlines is at the other end on 82.1%, a gap of 3 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 PDX to SEA?
The 5am–8am departure window is the strongest at 90.7% on time. The 8am–11am window is the weakest at 80.6%, 10 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 August delays on PDX to SEA?
August is the weakest month at 74.6% on time, compared with 91.2% in February. Across the year that is 17 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 PDX — the return legseparate record
- Portland International (PDX) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on PDX to SEA89.6%
- SkyWest Airlines on PDX to SEA85.5%
- Alaska Airlines on PDX to SEA82.1%
- PDX to LAX, a related route86.6%
- LAX to SEA, a related route85.0%
- PDX to DEN, a related route82.3%
- Delta Air Lines on-time record89.6%
- SkyWest Airlines on-time record85.5%
- Alaska Airlines on-time record82.1%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. PDX to SEA and SEA to PDX are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.