Carrier route record
DLSEA→KOA
Delta Air Lines · Seattle to Kailua-Kona
- Flights
- 365
- Period
- September 2025 to August 2026
- Share of route
- 26%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on SEA to KOA lands a B, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by roughly 45 minutes on average. That rests on 365 flights, with a median arrival 5 minutes early.
The US average over the same twelve months is 77.3%, so there is little to separate Delta on SEA to KOA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.1%
Arrivals under 15 minutes late, of 356 completed flights
Avg delay
47 min
Across delayed arrivals only, not all flights
Cancelled
2.19%
National rate is 1.89%
Whole route
74.5%
Every carrier on SEA to KOA, 1,410 flights
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 5 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
Delta against every carrier on SEA to KOA
Delta flew 365 of the 1,410 flights on SEA to KOA, about 26% of it. Its 76.1% on time is 2 points better than the route as a whole, which runs 74.5%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Delta at 76.1% to Alaska at 73.9%.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines (this page) | 365 | 76.1% | 47 min | 2.19% | B |
| Alaska Airlines | 1,045 | 73.9% | 51 min | 1.15% | C |
Flight by flight
Delta flight numbers on SEA to KOA
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Departure window
When Delta runs best on this route
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 365 flights.
There are not enough flights in each departure window to split Delta's SEA to KOA record by time of day without the percentages moving on noise. The headline rate of 76.1% is the reliable figure here.
Across the year
Delta on SEA to KOA through the year
August is the worst month at 63.3% on time, 30 points below October, the best at 93.5%. 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 31 flights.
Across the week, Wednesday is the strongest day at 88.2% on time and Friday the weakest at 67.3%, a spread of 21 points.
Arrival by arrival
How late Delta on SEA to KOA runs when it is late
Delta on SEA to KOA often beats the schedule: 90 of 356 completed flights, 25%, arrived 15 minutes or more early. Most of the lateness is short. 45 of the 85 late arrivals were under half an hour behind, and 17 reached an hour or more.
- 15+ min early90 flights25.3%
- Within 15 min181 flights50.8%
- 15–29 min late45 flights12.6%
- 30–59 min late23 flights6.5%
- 1–2 hours late12 flights3.4%
- 2+ hours late5 flights1.4%
Scale runs 0% to 100%.
Share of 356 completed flights by arrival against schedule.
14 of 57 late departures made up the time and arrived on time, 25% of them. In the other direction, 42 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at KOA.
The worst days
Worst days for Delta on SEA to KOA
The latest arrival of the period was on 19 December 2025, 6 hours 33 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 19 December 2025 | 6 hours 33 minutes | Carrier |
| 7 December 2025 | 3 hours 28 minutes | Late-arriving aircraft |
| 24 April 2026 | 3 hours 3 minutes | Carrier |
| 10 February 2026 | 2 hours 39 minutes | Carrier |
| 11 May 2026 | 2 hours 3 minutes | Carrier |
Delay causes
Why Delta runs late on this route
National Airspace System accounts for 43% of the 3,951 delay minutes carriers reported here, and the remaining four split what is left.
- 43%National Airspace System
- 41%Carrier
- 16%Late-arriving aircraft
The largest share of delay minutes, 41%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,624 of the 3,951 delay minutes reported here. The split is drawn from 3,951 reported delay minutes.
43% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 1,700 minutes out of 3,951, against a national NAS share of 21%.
Cancellations sit at 2.19% against a national 1.89%, which is ordinary. Diversions add another 0.27%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.8% 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 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 89.5% on time across 365 flights, 13 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 13 points of difference.
One caution: this is a thin sample. 365 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 Delta on SEA to KOA
Put together: treat all of this as provisional. 365 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 76.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 356 completed flights over 12 months sit behind that.
Related
Where to go next
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.