Carrier route record

B6BOS→SEA

JetBlue Airways · Boston to Seattle

Flights: 247
Period: July 2025 to June 2026
Share of route: 10%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with JetBlue Airways.

JetBlue on BOS to SEA 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 a little over an hour behind schedule. That rests on 247 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,006 at 71.6% on time.

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

On time

75.6%

Arrivals under 15 minutes late, of 246 completed flights

Avg delay

72 min

Across delayed arrivals only, not all flights

Cancelled

0.40%

National rate is 1.81%

Whole route

71.4%

Every carrier on BOS to SEA, 2,461 flights

These figures cover 247 flights between July 2025 and June 2026. Beyond the headline rate, 12.6% 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

JetBlue against every carrier on BOS to SEA

JetBlue flew 247 of the 2,461 flights on BOS to SEA, about 10% of it. Its 75.6% on time is 4 points better than the route as a whole, which runs 71.4%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from JetBlue at 75.6% to Alaska at 70.5%.

The two carriers here are closely matched: about 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.

On-time performance by carrier on BOS to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
JetBlue Airways (this page)thin sample	247	75.6%	72 min	0.40%	B+
Delta Air Lines	1,006	71.6%	55 min	1.59%	C
Alaska Airlines	1,208	70.5%	50 min	1.16%	C

No carrier stands out. Delta tops the table at 71.6%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.

Departure window

When JetBlue runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 36 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am142 flights88.7%
8am–11am23 flights—
11am–2pm—
2pm–5pm—
5pm–8pm82 flights52.4%
8pm–5am—

Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 52.4% on time, against 88.7% for the 5am–8am 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 5am–8am window is the busiest, with 142 flights scheduled in it.

Across the year

JetBlue on BOS to SEA through the year

Jul–Sep 2025156 flights72.9%
Oct–Dec 202525 flights—
Apr–Jun 202666 flights77.3%

Scale runs 65% to 85%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 75.6% on time across 247 flights.

Split by quarter, JetBlue on BOS to SEA logged 156 flights in Jul–Sep 2025, 25 flights in Oct–Dec 2025 and 66 flights in Apr–Jun 2026. Fewer than three of those quarters carried the 30 completed flights this site needs before printing a rate, so the 75.6% annual figure is the one to use.

Across the week, Monday is the strongest day at 85.7% on time and Sunday the weakest at 65.7%. 20 points is a smaller lever than departure hour, but it is free.

Delay causes

Why JetBlue runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 45% of the 4,331 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.

Late-arriving aircraft
45%
National Airspace System
26%
Carrier
24%
Extreme weather
3%
Security
1%

45% 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 4,331 reported delay minutes here, that single category outweighs weather by 14 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 4,331 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 88.7% on time here.

Cancellations are rare at 0.40%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.6% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

At 2,496 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 51.2% on time across 247 flights, 24 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 24 points of difference.

One caution: this is a thin sample. 247 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking JetBlue on BOS to SEA

Put together: treat all of this as provisional. 247 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 75.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 246 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures