Carrier route record

B6SEA→BOS

JetBlue Airways · Seattle to Boston

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 SEA to BOS earns an F+, which is as low as this site's scale goes for a reason. Only 51.2% of flights arrive inside the 15-minute window, 26 points worse than the national rate of 77.6%. Late arrivals average close to two hours. Treat any tight connection here as a coin flip. That rests on 247 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,005 at 81.2% on time.

The national on-time rate over the same period is 77.6%, so JetBlue on SEA to BOS runs 26 points behind the country as a whole. Across a thousand flights that is about 264 extra late arrivals.

On time

51.2%

Arrivals under 15 minutes late, of 244 completed flights

Avg delay

121 min

Across delayed arrivals only, not all flights

Cancelled

0.40%

National rate is 1.81%

Whole route

74.5%

Every carrier on SEA to BOS, 2,459 flights

These figures cover 247 flights between July 2025 and June 2026. Beyond the headline rate, 24.6% 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 SEA to BOS

JetBlue flew 247 of the 2,459 flights on SEA to BOS, about 10% of it. Its 51.2% on time is 23 points worse than the route as a whole, which runs 74.5%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from Delta at 81.2% to JetBlue at 51.2%.

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.2% of the time; Alaska Airlines manages 73.7%. Sample sizes sit next to every figure, because a two-point gap across 1,207 flights means less than a ten-point one.

On-time performance by carrier on SEA to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,005	81.2%	68 min	1.49%	B
Alaska Airlines	1,207	73.7%	48 min	0.99%	C+
JetBlue Airways (this page)thin sample	247	51.2%	121 min	0.40%	F+

Delta leads Alaska by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Departure window

When JetBlue runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 247 flights.

5am–8am—
8am–11am—
11am–2pm165 flights52.5%
2pm–5pm—
5pm–8pm—
8pm–5am82 flights48.8%

Scale runs 40% to 60%. Rows with fewer than 30 flights show a dash.

The 11am–2pm window is the strongest at 52.5% on time. The full set of windows spans 4 points.

Across the year

JetBlue on SEA to BOS through the year

Jul–Sep 2025156 flights52.9%
Oct–Dec 202525 flights—
Apr–Jun 202666 flights34.8%

Scale runs 25% to 60%. 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 51.2% on time across 247 flights.

Split by quarter, JetBlue on SEA to BOS 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 51.2% annual figure is the one to use.

Across the week, Wednesday is the strongest day at 55.9% on time and Sunday the weakest at 41.2%. 15 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. Carrier accounts for 54% of the 14,000 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.

Carrier
54%
Late-arriving aircraft
31%
National Airspace System
15%
Security
0%

The largest share of delay minutes, 54%, 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 7,847 of the 14,000 delay minutes reported here. The split is drawn from 14,444 reported delay minutes.

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. 24.6% 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 75.6% on time across 247 flights, 24 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 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 SEA to BOS

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 51.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 244 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