Route reliability record
KOA→SEA
Kailua-Kona to Seattle
- Flights
- 1,422
- Period
- July 2025 to June 2026
- Distance
- 2,688 mi
- Carriers
- 2
This route 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 77.6%. When something does go wrong the average delay runs about an hour. That rests on 1,422 KOA to SEA flights, of which Delta Air Lines flew 365 at 91.5% on time.
Best time to fly KOA to SEA: a 8am–11am departure, ideally on a Tuesday. Flights in that window arrived on time 89.2% of the time and Tuesday flights 90.3%, against 87.2% for the route overall.
Set against the rest of the country, this route's record is 10 points better than the US average of 77.6%. That gap is worth roughly 96 fewer late arrivals for every thousand flights.
Key figures
On time
87.2%
Arrivals under 15 minutes late, of 1,391 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
2.18%
National rate is 1.81%
Best carrier
Delta
91.5% on time across 365 flights
These figures cover 1,422 flights between July 2025 and June 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.
Carrier by carrier
Which airline is most reliable on KOA to SEA
The two carriers here are closely matched: 6 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 Lines | 365 | 91.5% | 46 min | 2.74% | A |
| Alaska Airlines | 1,057 | 85.7% | 60 min | 1.99% | A |
No carrier stands out. Delta tops the table at 91.5%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on KOA 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.
Best ways to make this trip
The most reliable ways to fly Kailua-Kona 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. KOA → SEAKailua-Kona to Seattle | Delta Air Lines | 89.0% | 91.5% | 2.74% | 8pm–5am, Tue | DL 485 20:50 |
| 2. KOA → SEAKailua-Kona to Seattle | Alaska Airlines | 84.0% | 85.7% | 1.99% | 8am–11am, Wed | — |
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 is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 1,422 flights.
- 5am–8am10 flights—
- 8am–11am412 flights89.2%
- 11am–2pm275 flights81.0%
- 2pm–5pm1 flights—
- 5pm–8pm—
- 8pm–5am724 flights88.7%
Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 81.0% on time against 89.2% for 8am–11am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 8pm–5am window is the busiest, with 724 flights scheduled in it.
Across the year
When delays peak on this route
Twelve months, one bar each, drawn from the same 1,422 flights. The strip shows how much of this route's record is set by the calendar rather than by the operation.
December is the weak month at 82.1% on time, against 93.6% in April. 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. January was the busiest month here, with 124 flights.
Across the week, Tuesday is the strongest day at 90.3% on time and Monday the weakest at 84.0%. 6 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 10,000 reported delay minutes.
- 39%Late-arriving aircraft
- 30%Carrier
- 28%National Airspace System
- 3%Extreme weather
- 0%Security
39% 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 10,000 reported delay minutes here, that single category outweighs weather by 14 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 10,313 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.2% on time here.
Cancellations sit at 2.18% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually 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.
At 2,688 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 72.8% on time across 1,421 flights, 14 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 14 points of difference.
The sample behind these figures is 1,422 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: take the 8am–11am departure, avoid December if the dates are flexible, and if two carriers are within a few dollars of each other, Delta is the one with the record behind it. None of that guarantees an on-time arrival; it moves the odds by 8 points, which is the most any booking decision can do. 1,391 completed flights over 12 months sit behind that.
Common questions
KOA to SEA questions
How often is KOA to SEA delayed?
About one flight in eight arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 12.8% of the 1,422 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on KOA to SEA?
Delta Air Lines leads at 91.5% on time across 365 flights. Alaska Airlines is at the other end on 85.7%, a gap of 6 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 KOA to SEA?
The 8am–11am departure window is the strongest at 89.2% on time. The 11am–2pm window is the weakest at 81.0%, 8 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 KOA to SEA?
December is the weakest month at 82.1% on time, compared with 93.6% in April. Across the year that is 12 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 KOA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on KOA to SEA91.5%
- Alaska Airlines on KOA to SEA85.7%
- KOA to HNL, a related route85.1%
- LAX to SEA, a related route85.4%
- KOA to LAX, a related route86.8%
- Delta Air Lines on-time record91.5%
- Alaska Airlines on-time record85.7%
- 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. KOA to SEA and SEA to KOA 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.