Flight number record

B6 434

JetBlue Airways · San Francisco to Boston

Route: SFO → BOS
Departs: 06:00
Flights: 327
Period: September 2025 to August 2026

Historical statistics for September 2025 to August 2026, not live status. For today’s B6 434, check with JetBlue Airways.

B6 434 earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 327 flights, with a median arrival 11 minutes early.

Set against the rest of the country, B6 434's record is 8 points better than the US average of 77.3%. That gap is worth roughly 79 fewer late arrivals for every thousand flights.

On time

85.2%

Arrivals under 15 minutes late, of 318 completed flights

Avg delay

71 min

Across delayed arrivals only, not all flights

Cancelled

2.75%

National rate is 1.89%

1 hour+ late

6.3%

National rate is 8.3%

These figures cover 327 flights between September 2025 and August 2026. The median arrival is 11 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.

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Schedule

When B6 434 flies

B6 434 flies SFO to BOS without a single fixed slot. Its most common scheduled departure was 06:00, used on 103 of 327 flights, with 07:10 (45 flights) and 08:15 (43 flights) next.

Departs 06:00103 flights31.5%
Departs 07:1045 flights13.8%
Departs 08:1543 flights13.1%

Scale runs 0% to 100%.

Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.

A 06:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and B6 434 runs 4 points worse at 85.2%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

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Against the route

B6 434 next to SFO to BOS

Every carrier on SFO to BOS combined arrived on time 74.5% of the time across 4,815 flights, so B6 434 is 11 points ahead of it. JetBlue flew 1,806 flights on the same city pair under all its flight numbers, including this one, and those ran 71.5% on time. Across its whole network JetBlue Airways managed 71.3%, which this flight beats by 14 points.

B6 434 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
B6 434thin sample	327	85.2%	71 min	2.75%	A
All JetBlue Airways on SFO–BOS	1,806	71.5%	78 min	2.77%	C
All carriers on SFO–BOS	4,815	74.5%	74 min	1.81%	C
JetBlue Airways, whole network	240,615	71.3%	77 min	3.56%	C−

Across the year

B6 434 quarter by quarter

B6 434 did not run the same all year. Its best quarter was Jan–Mar 2026 at 93.2% on time and its weakest Oct–Dec 2025 at 73.1%, a swing of 20 points on roughly 82 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Jul–Sep 202526 flights—
Oct–Dec 202578 flights73.1%
Jan–Mar 202677 flights93.2%
Apr–Jun 202684 flights84.5%
Jul–Sep 202662 flights93.0%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, B6 434 did best on Sunday at 91.8% on time and worst on Tuesday at 78.4%. Each day rests on about 47 flights, so a gap of 13 points is worth noticing but could still narrow in another year.

Arrival by arrival

How late B6 434 runs when it is late

B6 434 often beats the schedule: 132 of 318 completed flights, 42%, arrived 15 minutes or more early. The 47 late arrivals split 17 under half an hour, 10 between 30 and 60 minutes, and 20 an hour or more.

15+ min early132 flights41.5%
Within 15 min139 flights43.7%
15–29 min late17 flights5.3%
30–59 min late10 flights3.1%
1–2 hours late11 flights3.5%
2+ hours late9 flights2.8%

Scale runs 0% to 100%.

Share of 318 completed flights by arrival against schedule.

5 of 37 late departures made up the time and arrived on time, 14% of them. 15 flights left on time and still arrived late.

The worst days

Worst days for B6 434

The latest arrival of the period was on 24 December 2025, 3 hours 44 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. Three of the five worst days fell in December 2025.

The latest arrivals of B6 434 in the period
Date	Arrived late by	Largest filed cause
24 December 2025	3 hours 44 minutes	Late-arriving aircraft
24 September 2025	3 hours 39 minutes	National Airspace System
23 December 2025	3 hours 21 minutes	Late-arriving aircraft
5 March 2026	3 hours 12 minutes	Late-arriving aircraft
16 December 2025	2 hours 46 minutes	Carrier

Delay causes

Why B6 434 runs late

National Airspace System accounts for 45% of the 3,337 delay minutes carriers reported here, and the remaining four split what is left.

National Airspace System
45%
Carrier
31%
Late-arriving aircraft
24%

45% 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 1,492 minutes out of 3,337, against a national NAS share of 21%. The split is drawn from 3,337 delay minutes reported on B6 434.

Cancellations run at 2.75%, against 1.89% nationally. That is roughly one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and routes

What a delay on this flight costs

6.3% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.

At 2,704 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.

Every one of the 327 flights under B6 434 in the data flew SFO to BOS. The number was not reused on any other city pair, which makes this a clean record of one route.

One caution: this is a thin sample. 327 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 B6 434

For a booking, the cancellation rate is the figure to plan around on B6 434: 2.75% of its 327 scheduled flights did not operate. A late arrival costs a little over an hour, but a cancellation costs the day, so leave a later option open.

Where to go next

A flight number here means JetBlue Airways’s own number as it reports to the DOT. How the figures are computed is on the methodology page.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures