Route reliability record
SEA→EWR
Seattle to Newark
- Flights
- 2,235
- Period
- July 2025 to June 2026
- Distance
- 2,402 mi
- Carriers
- 2
This route lands a B, 4 points better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 2,235 flights, of which United Airlines flew 997 at 81.4% 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.
Key figures
On time
81.2%
Arrivals under 15 minutes late, of 2,187 completed flights
Avg delay
69 min
Across delayed arrivals only, not all flights
Cancelled
1.74%
National rate is 1.81%
Best carrier
United
81.4% on time across 997 flights
These figures cover 2,235 flights between July 2025 and June 2026. The median arrival is 13 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 EWR
The two carriers here are closely matched: half a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 997 | 81.4% | 88 min | 1.10% | B |
| Alaska Airlines | 1,238 | 81.0% | 54 min | 2.26% | B |
No carrier stands out. United tops the table at 81.4%, half a point clear of the bottom, which is inside the range this kind of sample moves year to year.
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 half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am531 flights92.6%
- 8am–11am593 flights76.1%
- 11am–2pm247 flights68.4%
- 2pm–5pm204 flights74.9%
- 5pm–8pm—
- 8pm–5am660 flights83.2%
Scale runs 60% to 100%. 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 68.4% on time against 92.6% 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 660 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 29 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 60.7% on time, 29 points below April, the best at 89.5%. 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. August was the busiest month here, with 229 flights.
Across the week, Tuesday is the strongest day at 87.0% on time and Sunday the weakest at 78.1%. 9 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 49% of the 28,000 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.
- 49%National Airspace System
- 26%Carrier
- 19%Late-arriving aircraft
- 6%Extreme weather
- 0%Security
49% 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 28,000, against a national NAS share of 21%. The split is drawn from 28,382 reported delay minutes.
Cancellations sit at 1.74% against a national 1.81%, which is ordinary. Diversions add another 0.40%.
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 a little over 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 73.5% on time across 2,234 flights, 8 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 8 points of difference.
The sample behind these figures is 2,235 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 89.5% on time and July 60.7%, a swing of 29 points. If the dates move at all, move them out of July before you think about anything else. 2,187 completed flights over 12 months sit behind that.
Common questions
SEA to EWR questions
How often is SEA to EWR delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.8% of the 2,235 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on SEA to EWR?
United Airlines leads at 81.4% on time across 997 flights. Alaska Airlines is at the other end on 81.0%, a gap of half a point. 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 EWR?
The 5am–8am departure window is the strongest at 92.6% on time. The 11am–2pm window is the weakest at 68.4%, 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 EWR?
July is the weakest month at 60.7% on time, compared with 89.5% in April. Across the year that is 29 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
- EWR to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Newark Liberty International (EWR) delay statistics
- United Airlines on-time record81.4%
- Alaska Airlines on-time record81.0%
- 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 EWR and EWR 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.