Route reliability record
SEA→KOA
Seattle to Kailua-Kona
- Flights
- 1,421
- Period
- July 2025 to June 2026
- Distance
- 2,688 mi
- Carriers
- 2
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 1,421 SEA to KOA flights, of which Delta Air Lines flew 365 at 78.5% on time.
Best time to fly SEA to KOA: a 2pm–5pm departure, ideally on a Wednesday. Flights in that window arrived on time 80.5% of the time and Wednesday flights 77.6%, against 72.8% for the route overall.
The national on-time rate over the same period is 77.6%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 48 extra late arrivals.
Key figures
On time
72.8%
Arrivals under 15 minutes late, of 1,391 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
1.13%
National rate is 1.81%
Best carrier
Delta
78.5% on time across 365 flights
These figures cover 1,421 flights between July 2025 and June 2026. The median arrival is 3 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 SEA to KOA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 78.5% of the time; Alaska Airlines manages 70.9%. Sample sizes sit next to every figure, because a two-point gap across 1,056 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 365 | 78.5% | 51 min | 1.64% | B |
| Alaska Airlines | 1,056 | 70.9% | 51 min | 0.95% | C+ |
Delta leads Alaska by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on SEA to KOA
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 Seattle to Kailua-Kona
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. SEA → KOASeattle to Kailua-Kona | Delta Air Lines | 77.2% | 78.5% | 1.64% | 2pm–5pm, Wed | DL 340 14:20 |
| 2. SEA → KOASeattle to Kailua-Kona | Alaska Airlines | 70.2% | 70.9% | 0.95% | 2pm–5pm, Mon | — |
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 12 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1 flights—
- 8am–11am315 flights69.7%
- 11am–2pm309 flights68.8%
- 2pm–5pm474 flights80.5%
- 5pm–8pm322 flights68.3%
- 8pm–5am—
Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 2pm–5pm slot at 80.5% on time, ahead of 5pm–8pm at 68.3%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 2pm–5pm window is the busiest, with 474 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 37 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.
July is the worst month at 57.0% on time, 37 points below April, the best at 93.7%. 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. January was the busiest month here, with 124 flights.
Across the week, Wednesday is the strongest day at 77.6% on time and Friday the weakest at 64.8%. 13 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 19,000 reported delay minutes.
- 40%Carrier
- 30%National Airspace System
- 29%Late-arriving aircraft
- 2%Extreme weather
The largest share of delay minutes, 40%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 7,774 of the 19,000 delay minutes reported here. The split is drawn from 19,377 reported delay minutes.
Cancellations sit at 1.13% against a national 1.81%, which is ordinary. Diversions add another 0.99%.
Connections and stage length
What a delay here actually costs
7.0% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 50 minutes, which a normal layover absorbs.
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 87.2% on time across 1,422 flights, 14 points above 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 1,421 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 KOA 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. April runs 93.7% on time and July 57.0%, a swing of 37 points. If the dates move at all, move them out of July before you think about anything else. 1,391 completed flights over 12 months sit behind that.
Common questions
SEA to KOA questions
How often is SEA to KOA delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.2% of the 1,421 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 50 minutes on average.
Which airline is most reliable on SEA to KOA?
Delta Air Lines leads at 78.5% on time across 365 flights. Alaska Airlines is at the other end on 70.9%, a gap of 8 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 SEA to KOA?
The 2pm–5pm departure window is the strongest at 80.5% on time. The 5pm–8pm window is the weakest at 68.3%, 12 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 July delays on SEA to KOA?
July is the weakest month at 57.0% on time, compared with 93.7% in April. Across the year that is 37 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
- KOA to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on SEA to KOA78.5%
- Alaska Airlines on SEA to KOA70.9%
- SEA to LAX, a related route83.4%
- HNL to KOA, a related route86.1%
- SEA to PHX, a related route79.2%
- Delta Air Lines on-time record78.5%
- Alaska Airlines on-time record70.9%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to KOA and KOA to SEA 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.