Route reliability record
JFK→SEA
New York to Seattle
- Flights
- 2,906
- Period
- July 2025 to June 2026
- Distance
- 2,422 mi
- Carriers
- 3
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, 8 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 2,906 flights, of which Delta Air Lines flew 1,338 at 73.2% on time.
The national on-time rate over the same period is 77.6%, so this route runs 8 points behind the country as a whole. Across a thousand flights that is about 79 extra late arrivals.
Key figures
On time
69.7%
Arrivals under 15 minutes late, of 2,819 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
2.58%
National rate is 1.81%
Best carrier
Delta
73.2% on time across 1,338 flights
These figures cover 2,906 flights between July 2025 and June 2026. Beyond the headline rate, 8.8% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on JFK to SEA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 73.2% of the time; Alaska Airlines manages 66.2%. Sample sizes sit next to every figure, because a two-point gap across 1,402 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,338 | 73.2% | 57 min | 2.32% | C |
| JetBlue Airwaysthin sample | 166 | 71.3% | 98 min | 1.20% | C |
| Alaska Airlines | 1,402 | 66.2% | 61 min | 3.00% | C |
Delta leads Alaska by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 17 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am686 flights71.5%
- 8am–11am39 flights75.7%
- 11am–2pm578 flights80.1%
- 2pm–5pm626 flights67.6%
- 5pm–8pm928 flights63.0%
- 8pm–5am49 flights68.8%
Scale runs 55% to 85%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 63.0% on time, against 80.1% for the 11am–2pm slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5pm–8pm window is the busiest, with 928 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 46 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 38.2% on time, against 83.9% in September. 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. July was the busiest month here, with 279 flights.
Across the week, Saturday is the strongest day at 72.4% on time and Sunday the weakest at 66.2%. 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. National Airspace System accounts for 43% of the 52,000 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.
- 43%National Airspace System
- 28%Carrier
- 22%Late-arriving aircraft
- 6%Extreme weather
- 1%Security
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 22,000 minutes out of 52,000, against a national NAS share of 21%. The split is drawn from 52,354 reported delay minutes.
Cancellations run at 2.58%, against 1.81% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and stage length
What a delay here actually costs
8.8% 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 are the about an hour kind, which a normal layover absorbs.
At 2,422 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 75.3% on time across 2,906 flights, 6 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 6 points of difference.
The sample behind these figures is 2,906 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. September runs 83.9% on time and December 38.2%, a swing of 46 points. If the dates move at all, move them out of December before you think about anything else. 2,819 completed flights over 12 months sit behind that.
Common questions
JFK to SEA questions
How often is JFK to SEA delayed?
Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 30.3% of the 2,906 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on JFK to SEA?
Delta Air Lines leads at 73.2% on time across 1,338 flights. Alaska Airlines is at the other end on 66.2%, a gap of 7 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 JFK to SEA?
The 11am–2pm departure window is the strongest at 80.1% on time. The 5pm–8pm window is the weakest at 63.0%, 17 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 JFK to SEA?
December is the weakest month at 38.2% on time, compared with 83.9% in September. Across the year that is 46 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 JFK — the return legseparate record
- John F. Kennedy International (JFK) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on-time record73.2%
- JetBlue Airways on-time record71.3%
- Alaska Airlines on-time record66.2%
- What a cancellation rate actually tells you (and what it hides)
- The best time of day to fly, according to 7.04 million flight records
Direction matters. JFK to SEA and SEA to JFK 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.