Route reliability record
EWR→SEA
Newark to Seattle
- Flights
- 2,234
- Period
- July 2025 to June 2026
- Distance
- 2,402 mi
- Carriers
- 2
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 2,234 flights, of which United Airlines flew 997 at 77.1% on time.
The national on-time rate over the same period is 77.6%, so this route runs 4 points behind the country as a whole. Across a thousand flights that is about 41 extra late arrivals.
Key figures
On time
73.5%
Arrivals under 15 minutes late, of 2,185 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
2.01%
National rate is 1.81%
Best carrier
United
77.1% on time across 997 flights
These figures cover 2,234 flights between July 2025 and June 2026. Beyond the headline rate, 8.6% 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 EWR to SEA
The choice of carrier is not cosmetic here. United Airlines arrives on time 77.1% of the time; Alaska Airlines manages 70.6%. Sample sizes sit next to every figure, because a two-point gap across 1,237 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 997 | 77.1% | 61 min | 1.00% | B |
| Alaska Airlines | 1,237 | 70.6% | 66 min | 2.83% | C |
United 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 22 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am485 flights78.9%
- 8am–11am346 flights82.7%
- 11am–2pm49 flights85.7%
- 2pm–5pm444 flights78.6%
- 5pm–8pm718 flights63.6%
- 8pm–5am192 flights65.2%
Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 63.6% on time, against 85.7% 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 718 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 45.4% on time, against 91.0% 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. August was the busiest month here, with 229 flights.
Across the week, Thursday is the strongest day at 75.6% on time and Sunday the weakest at 69.7%. 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 37,000 reported delay minutes.
- 38%National Airspace System
- 36%Late-arriving aircraft
- 18%Carrier
- 7%Extreme weather
- 1%Security
36% 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 37,000 reported delay minutes here, that single category outweighs weather by 5 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 36,881 reported delay minutes.
38% 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 14,000 minutes out of 37,000, against a national NAS share of 21%.
Cancellations sit at 2.01% against a national 1.81%, which is ordinary. Diversions add another 0.18%.
Connections and stage length
What a delay here actually costs
8.6% 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 2,402 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 81.2% on time across 2,235 flights, 8 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 8 points of difference.
The sample behind these figures is 2,234 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. April runs 91.0% on time and December 45.4%, a swing of 46 points. If the dates move at all, move them out of December before you think about anything else. 2,185 completed flights over 12 months sit behind that.
Common questions
EWR to SEA questions
How often is EWR to SEA 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 26.5% of the 2,234 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on EWR to SEA?
United Airlines leads at 77.1% on time across 997 flights. Alaska Airlines is at the other end on 70.6%, 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 EWR to SEA?
The 11am–2pm departure window is the strongest at 85.7% on time. The 5pm–8pm window is the weakest at 63.6%, 22 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 EWR to SEA?
December is the weakest month at 45.4% on time, compared with 91.0% in April. 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 EWR — the return legseparate record
- Newark Liberty International (EWR) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- United Airlines on-time record77.1%
- Alaska Airlines on-time record70.6%
- 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. EWR to SEA and SEA to EWR 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.