Route reliability record
EWR→SEA
Newark to Seattle
- Flights
- 2,263
- Period
- September 2025 to August 2026
- Distance
- 2,402 mi
- Carriers
- 2
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, 4 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 2,263 EWR to SEA flights, of which United Airlines flew 990 at 74.5% on time.
Best time to fly EWR to SEA: a 11am–2pm departure, ideally on a Thursday. Flights in that window arrived on time 83.5% of the time and Thursday flights 77.4%, against 72.9% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 4 points behind the country as a whole. Across a thousand flights that is about 44 extra late arrivals.
Key figures
On time
72.9%
Arrivals under 15 minutes late, of 2,206 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
2.39%
National rate is 1.89%
Best carrier
United
74.5% on time across 990 flights
These figures cover 2,263 flights between September 2025 and August 2026. Beyond the headline rate, 9.1% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on EWR to SEA
The two carriers here are closely matched: 3 points 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 | 990 | 74.5% | 70 min | 1.82% | C |
| Alaska Airlines | 1,273 | 71.6% | 71 min | 2.83% | C |
No carrier stands out. United tops the table at 74.5%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on EWR to SEA
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Newark to Seattle
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 2 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. EWR → SEANewark to Seattle | United Airlines | 73.1% | 74.5% | 1.82% | 5am–8am, Sat | UA 1330 08:50 |
| 2. EWR → SEANewark to Seattle | Alaska Airlines | 69.6% | 71.6% | 2.83% | 8am–11am, Thu | AS 299 07:25 |
| 3. JFK → SEANew York to Seattle | Delta Air Lines | 69.1% | 71.4% | 3.21% | 11am–2pm, Fri | DL 699 07:00 |
| 4. JFK → SEANew York to Seattle | Alaska Airlines | 65.8% | 68.1% | 3.35% | 11am–2pm, Sat | AS 23 11:30 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 3 points between the best and worst carrier.
- 5am–8am430 flights76.9%
- 8am–11am408 flights81.6%
- 11am–2pm98 flights83.5%
- 2pm–5pm425 flights77.6%
- 5pm–8pm649 flights64.2%
- 8pm–5am253 flights61.9%
Scale runs 55% to 90%.
The 8pm–5am window is where this operation falls apart: 61.9% on time, against 83.5% 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 649 flights scheduled in it.
Explore
Filter EWR to SEA by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On EWR to SEA, the best departure window is 11am–2pm at 83.5% on time and the worst is 8pm–5am at 61.9%, a wide gap of 21.6 points. All US flights leaving 11am–2pm ran 78.3%.
- 5–8am76.9%
- 8–11am81.6%
- 11am–2pm83.5%
- 2–5pm77.6%
- 5–8pm64.2%
- 8pm–5am61.9%
best all US flightsScale 55% to 95%.
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. July was the busiest month here, with 246 flights.
Across the week, Thursday is the strongest day at 77.4% on time and Friday the weakest at 68.0%, a spread of 9 points.
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 42,000 reported delay minutes.
- 37%National Airspace System
- 32%Late-arriving aircraft
- 19%Carrier
- 11%Extreme weather
- 1%Security
Extreme weather accounts for 11% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 1.9 times the usual weather exposure. The split is drawn from 42,134 reported delay minutes.
37% 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 16,000 minutes out of 42,000, against a national NAS share of 21%.
Cancellations sit at 2.39% against a national 1.89%, which is ordinary. Diversions add another 0.13%.
Connections and stage length
What a delay here actually costs
9.1% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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 83.4% on time across 2,264 flights, 11 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 11 points of difference.
The sample behind these figures is 2,263 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.
Work out the risk of missing a connection in SEA after this flight
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. 2,206 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 arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.1% of the 2,263 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on EWR to SEA?
United Airlines leads at 74.5% on time across 990 flights. Alaska Airlines is at the other end on 71.6%, a gap of 3 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 83.5% on time. The 8pm–5am window is the weakest at 61.9%, 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 EWR to SEA74.5%
- Alaska Airlines on EWR to SEA71.6%
- EWR to MCO, a related route77.9%
- LAX to SEA, a related route85.0%
- EWR to ATL, a related route76.9%
- United Airlines on-time record74.5%
- Alaska Airlines on-time record71.6%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 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.
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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.