Flight number record

B6 434

JetBlue Airways · San Francisco to Boston

Route: SFO → BOS
Departs: 06:05
Flights: 319
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 319 flights, with a median arrival 12 minutes early.

Set against the rest of the country, B6 434's record is 8 points better than the US average of 77.6%. That gap is worth roughly 75 fewer late arrivals for every thousand flights.

On time

85.1%

Arrivals under 15 minutes late, of 315 completed flights

Avg delay

71 min

Across delayed arrivals only, not all flights

Cancelled

1.25%

National rate is 1.81%

1 hour+ late

6.3%

National rate is 8.1%

These figures cover 319 flights between July 2025 and June 2026. The median arrival is 12 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.

Schedule

When B6 434 flies

B6 434 flies SFO to BOS without a single fixed slot. Its most common scheduled departure was 06:05, used on 56 of 319 flights, with 07:10 (45 flights) and 08:15 (43 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 06:0556 flights17.6%
Departs 07:1045 flights14.1%
Departs 08:1543 flights13.5%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

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

A 06:05 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 85.1%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

B6 434 next to SFO to BOS

Every carrier on SFO to BOS combined arrived on time 76.9% of the time across 4,674 flights, so B6 434 is 8 points ahead of it. JetBlue flew 1,674 flights on the same city pair under all its flight numbers, including this one, and those ran 75.4% on time. Across its whole network JetBlue Airways managed 72.7%, which this flight beats by 12 points.

B6 434 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
B6 434thin sample	319	85.1%	71 min	1.25%	A
All JetBlue Airways on SFO–BOS	1,674	75.4%	76 min	1.79%	B
All carriers on SFO–BOS	4,674	76.9%	74 min	1.35%	B
JetBlue Airways, whole network	234,468	72.7%	76 min	2.56%	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 80 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 202580 flights90.0%
Oct–Dec 202578 flights73.1%
Jan–Mar 202677 flights93.2%
Apr–Jun 202684 flights84.5%

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

By weekday, B6 434 did best on Friday at 92.3% on time and worst on Thursday at 78.4%. Each day rests on about 46 flights, so a gap of 14 points is worth noticing but could still narrow in another year.

Delay causes

Why B6 434 runs late

One category carries most of the weight here. National Airspace System accounts for 45% of the 3,344 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.

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 1,500 minutes out of 3,344, against a national NAS share of 21%. The split is drawn from 3,344 delay minutes reported on B6 434.

Cancellations sit at 1.25% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and routes

What a delay on this flight costs

6.3% of arrivals land an hour or more late, close to the national 8.1%. 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 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 319 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. 319 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, B6 434 has one of the better records a US domestic flight can show: 85.1% on time and 1.25% cancelled. That is a base rate, not a promise about any single day.

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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures