Route reliability record

SEA→JFK

Seattle to New York

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 B. Close to three flights in four arrive on time by the DOT's definition, 2 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 1,337 at 79.6% on time.

The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

75.3%

Arrivals under 15 minutes late, of 2,807 completed flights

Avg delay

62 min

Across delayed arrivals only, not all flights

Cancelled

2.41%

National rate is 1.81%

Best carrier

Delta

79.6% on time across 1,337 flights

These figures cover 2,906 flights between July 2025 and June 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.

Carrier by carrier

Which airline is most reliable on SEA to JFK

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 79.6% of the time; Alaska Airlines manages 71.6%. Sample sizes sit next to every figure, because a two-point gap across 1,403 flights means less than a ten-point one.

On-time performance by carrier on SEA to JFK
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,337	79.6%	70 min	2.39%	B
JetBlue Airwaysthin sample	166	72.0%	78 min	1.20%	C
Alaska Airlines	1,403	71.6%	54 min	2.57%	C

Delta leads Alaska by 8 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 24 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am505 flights89.8%
8am–11am337 flights80.7%
11am–2pm591 flights66.0%
2pm–5pm630 flights67.4%
5pm–8pm—
8pm–5am843 flights76.9%

Scale runs 60% 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 66.0% on time against 89.8% for 5am–8am. 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 843 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 40 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.

Darker means more delays. Figures are on-time percentages.February best, July worst

July is the worst month at 49.2% on time, 40 points below February, the best at 89.2%. 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. July was the busiest month here, with 279 flights.

Across the week, Tuesday is the strongest day at 78.7% on time and Sunday the weakest at 70.9%. 8 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 43,000 reported delay minutes.

National Airspace System
39%
Carrier
34%
Late-arriving aircraft
22%
Extreme weather
4%
Security
1%

39% 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 17,000 minutes out of 43,000, against a national NAS share of 21%. The split is drawn from 42,788 reported delay minutes.

The largest share of delay minutes, 34%, 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 15,000 of the 43,000 delay minutes reported here.

Cancellations sit at 2.41% against a national 1.81%, which is ordinary. Diversions add another 1.00%.

Connections and stage length

What a delay here actually costs

7.7% 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 69.7% on time across 2,906 flights, 6 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 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. February runs 89.2% on time and July 49.2%, a swing of 40 points. If the dates move at all, move them out of July before you think about anything else. 2,807 completed flights over 12 months sit behind that.

Common questions

SEA to JFK questions

How often is SEA to JFK delayed?

About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.7% 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 SEA to JFK?

Delta Air Lines leads at 79.6% on time across 1,337 flights. Alaska Airlines is at the other end on 71.6%, 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 JFK?

The 5am–8am departure window is the strongest at 89.8% on time. The 11am–2pm window is the weakest at 66.0%, 24 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 JFK?

July is the weakest month at 49.2% on time, compared with 89.2% in February. Across the year that is 40 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. SEA to JFK and JFK to SEA 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.

Key figures