Route profile
SFO→BOS
Flight reliability, delays and best times to fly from San Francisco to Boston, 2,704 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 45% of comparable major US routes (4,598 compared)
Calculated from 14,227 flights. How this is calculated
SFO → BOS arrives on time 77.9% of the time; the return trip, BOS → SFO, arrives on time 74.6% of the time, a 3.3-point gap between the two directions of the same city pair.
SFO → BOS spends 30.0 minutes on the ground on a 2,704-mile trip: 21.3 minutes from pushback to wheels-up at SFO and 8.7 minutes from touchdown to gate at BOS.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
This route holds up about the same all year, a steadier seasonal pattern than 94% of 3,357 comparable routes.
83.3% on time in its best month (November) against 73.3% in its worst (July).
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 3,357 in the comparison.
Why SFO → BOS flights are cancelled
July 2023 – July 2026
SFO → BOS cancelled 148 of 14,227 scheduled flights — about 1 in every 96. The reason filed most often was the airline, 50.0% of the cancellations coded on this route — about 1 in every 192 scheduled flights.
Share of cancellations
Of 148 cancelled departures carrying a reason code.
What each reason means
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
74 cancellations, 50.0% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
53 cancellations, 35.8% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
21 cancellations, 14.2% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
148 coded cancellations were recorded on SFO → BOS; the section appears from 50.
When it goes wrong
July 2023 – July 2026
50 min late
against a median of 7 min early
Percentiles over 14,227 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at BOS after arriving from SFO.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 37% | Likely to miss |
| 45 min | 21% | High risk |
| 60 min | 15% | Some risk |
| 90 min | 8.3% | Some risk |
| 120 min | 5.0% | Some risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.04% of the time and diverts 0.25% of the time, which a late arrival never shows up in.
Chance of missing is the share of 14,043 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 50 minutes late (90th-percentile gate arrival delay), over 14,227 operations.
Any other layover length: connection checker.
Best time to fly
SFO → BOS flights departing 5–9 AM arrived on time 86.5% of the time, against 69.4% for 9 AM–12 PM departures, a gap of 17.1 percentage points.
By day and hour
On-time arrival rate for each weekday and scheduled departure hour, in local time at the departure airport (SFO).
Hour of departure matters more than day of the week: hourly averages sit a typical 6.5 points from the route-wide rate, weekday averages 3.2 points.
| Hour | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
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On-time rate, % · stronger color, fewer on time
- 60–64
- 65–69
- 70–74
- 75–79
- 80–84
- 85–89
- 90–94
- Fewer than 120 flights, not scored
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · On time is arrival within 15 minutes of schedule. Cells round to whole percentages; the table shows one decimal.
No slot is named best or worst: too few reach 500 flights. Departures before 7 AM (519 flights) are not drawn: no slot in those hours has enough flights to score.
View as tableHide table
| Hour | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday |
|---|---|---|---|---|---|---|---|
| 7 AM–8 AM | 87.0% on time275 flights | 89.9% on time272 flights | 91.9% on time273 flights | 85.9% on time272 flights | 89.2% on time274 flights | 88.1% on time256 flights | 87.5% on time276 flights |
| 8 AM–9 AM | 79.6% on time210 flights | 85.4% on time214 flights | 88.3% on time210 flights | 79.1% on time208 flights | 80.8% on time210 flights | 84.8% on time166 flights | 84.2% on time202 flights |
| 9 AM–10 AM | 37 flights, too few to score | 37 flights, too few to score | 39 flights, too few to score | 38 flights, too few to score | 38 flights, too few to score | 31 flights, too few to score | 40 flights, too few to score |
| 10 AM–11 AM | 63.5% on time137 flights | 68.5% on time130 flights | 75.8% on time128 flights | 62.2% on time130 flights | 64.6% on time130 flights | 105 flights, too few to score | 66.2% on time133 flights |
| 11 AM–12 PM | 62.1% on time155 flights | 69.7% on time154 flights | 73.3% on time161 flights | 67.5% on time161 flights | 68.3% on time162 flights | 116 flights, too few to score | 70.1% on time156 flights |
| 12 PM–1 PM | 68.2% on time154 flights | 69.0% on time147 flights | 73.9% on time154 flights | 64.2% on time151 flights | 77.5% on time144 flights | 77.2% on time125 flights | 68.5% on time153 flights |
| 1 PM–2 PM | 69.0% on time233 flights | 84.1% on time216 flights | 73.4% on time219 flights | 72.4% on time229 flights | 71.4% on time234 flights | 77.7% on time168 flights | 70.8% on time224 flights |
| 2 PM–3 PM | 70 flights, too few to score | 66 flights, too few to score | 66 flights, too few to score | 65 flights, too few to score | 69 flights, too few to score | 41 flights, too few to score | 70 flights, too few to score |
| 3 PM–4 PM | 79.0% on time143 flights | 77.5% on time139 flights | 75.4% on time138 flights | 66.9% on time145 flights | 70.5% on time147 flights | 68 flights, too few to score | 81.4% on time135 flights |
| 4 PM–5 PM | 48 flights, too few to score | 32 flights, too few to score | 35 flights, too few to score | 49 flights, too few to score | 52 flights, too few to score | 42 flights, too few to score | 45 flights, too few to score |
| 5 PM–6 PM | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 1 flight, too few to score | 0 flights, too few to score | 0 flights, too few to score |
| 6 PM–7 PM | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score |
| 7 PM–8 PM | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score | 0 flights, too few to score |
| 8 PM–9 PM | 95 flights, too few to score | 88 flights, too few to score | 99 flights, too few to score | 98 flights, too few to score | 100 flights, too few to score | 77 flights, too few to score | 103 flights, too few to score |
| 9 PM–10 PM | 77.0% on time189 flights | 81.2% on time133 flights | 74.5% on time147 flights | 70.7% on time192 flights | 75.5% on time191 flights | 83.3% on time133 flights | 75.8% on time190 flights |
| 10 PM–11 PM | 105 flights, too few to score | 84 flights, too few to score | 91 flights, too few to score | 108 flights, too few to score | 106 flights, too few to score | 64 flights, too few to score | 105 flights, too few to score |
| 11 PM–12 AM | 79.5% on time204 flights | 85.8% on time206 flights | 82.8% on time206 flights | 73.6% on time212 flights | 77.4% on time216 flights | 80.9% on time201 flights | 70.5% on time212 flights |
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 88.4% on time from 514 flights
- 7 AM: 88.5% on time from 1,898 flights
- 8 AM: 83.1% on time from 1,420 flights
- 9 AM: 71.4% on time from 260 flights
- 10 AM: 67.9% on time from 893 flights
- 11 AM: 70.2% on time from 1,065 flights
- 12 PM: 71.0% on time from 1,028 flights
- 1 PM: 73.9% on time from 1,523 flights
- 2 PM: 76.6% on time from 447 flights
- 3 PM: 75.5% on time from 915 flights
- 4 PM: 86.2% on time from 303 flights
- 5 PM to 7 PM: too few flights to score
- 8 PM: 81.4% on time from 660 flights
- 9 PM: 76.4% on time from 1,175 flights
- 10 PM: 73.6% on time from 663 flights
- 11 PM: 78.6% on time from 1,457 flights
Why SFO → BOS runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for SFO → BOS. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on SFO → BOS, at 36.0%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 86.5% of the time and 9 AM–12 PM departures 69.4%.
How this route holds up in bad weather
July 2023 – July 2026
The harder-hit end is BOS, where the flight lands. Its figure counts departures from BOS, so it says more about how that airport copes than about this route. Bad weather cancels 3.9 times the normal rate at BOS against 1.7 times at SFO. Cancelled in bad weather against normal hours: SFO 1.5% against 0.9%, BOS 5.3% against 1.4%. Flights that did leave BOS in bad weather arrived on time 65.1% of the time, against 79.7% in normal hours.
Bad weather and normal hours at the airports
Scheduled departures, July 2023 – July 2026| Departures from | SFO | BOS |
|---|---|---|
| Cancelled in bad weather | 1.5% | 5.3% |
| Cancelled in normal hours | 0.9% | 1.4% |
| Arrived on time, bad weather | 73.0% | 65.1% |
| Arrived on time, normal hours | 79.8% | 79.7% |
| Departures in bad weather | 36,006 | 60,840 |
United Airlines (1.0% cancelled against 1.9% for the other carriers at SFO) and Delta Air Lines (0.8% cancelled against 1.5% for the other carriers at SFO) cancelled fewer departures from SFO in bad weather than the other carriers there did in the same months. None of the route’s other carriers was clearly worse.
This route’s airlines in bad weather at SFO
All departures from SFO| Airline | Bad-weather departures | Cancelled | Other carriers |
|---|---|---|---|
| United Airlines | 13,903 | 1.0%below the others | 1.9% |
| Delta Air Lines | 3,513 | 0.8%below the others | 1.5% |
| JetBlue | 1,072 | 1.3%about level | 1.5% |
| Alaska Airlines | 3,124 | 1.8%about level | 1.4% |
These are airport figures, not route figures: every scheduled departure from SFO and BOS, to any destination, in hours the weather report called bad. The airline rows count each carrier’s departures from SFO on every route.
Weather source and limits. In full: SFO (airlines), BOS, What Weather Costs Each Airport, Who Cancels More When the Weather Turns, Airports That Change Places When Weather Turns.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| United Airlines | 5,526 | 79.4% | 1.01% | -8 min | 8.2% |
| JetBlue | 5,054 | 76.1% | 1.07% | -7 min | 9.6% |
| Delta Air Lines | 2,529 | 77.3% | 1.03% | -5 min | 7.8% |
| Alaska Airlines | 1,117 | 79.1% | 1.07% | -6 min | 5.8% |
United Airlines flew 38.8% of the 14,226 flights listed.
United Airlines arrived on time 3.3 percentage points more often than JetBlue on this route.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
DL400 (7:10 AM) arrived on time 90.4% of the time, 15.5 points more often than B61734 (12:20 PM) at 74.9%.
Weekly and seasonal patterns
By day of week
Saturday is historically the most reliable day and Thursday the least, a gap of 9.2 percentage points.
By month
- Jan: 80.9%
- Feb: 82.4%
- Mar: 78.9%
- Apr: 80.3%
- May: 74.5%
- Jun: 75.1%
- Jul: 73.3%
- Aug: 78.2%
- Sep: 74.1%
- Oct: 81.7%
- Nov: 83.3%
- Dec: 77.8%
July is historically the weakest month and November the strongest, a spread of 10.0 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 72.8% from 436 flights
- August 2023: 78.6% from 443 flights
- September 2023: 68.6% from 450 flights
- October 2023: 84.9% from 440 flights
- November 2023: 89.6% from 347 flights
- December 2023: 74.3% from 343 flights
- January 2024: 71.2% from 286 flights
- February 2024: 79.9% from 277 flights
- March 2024: 75.1% from 326 flights
- April 2024: 71.5% from 324 flights
- May 2024: 77.4% from 398 flights
- June 2024: 76.1% from 395 flights
- July 2024: 78.0% from 443 flights
- August 2024: 70.9% from 425 flights
- September 2024: 82.0% from 407 flights
- October 2024: 89.0% from 427 flights
- November 2024: 81.8% from 362 flights
- December 2024: 77.4% from 375 flights
- January 2025: 88.9% from 306 flights
- February 2025: 82.8% from 268 flights
- March 2025: 83.4% from 327 flights
- April 2025: 91.6% from 368 flights
- May 2025: 70.9% from 433 flights
- June 2025: 81.3% from 438 flights
- July 2025: 75.9% from 450 flights
- August 2025: 84.8% from 431 flights
- September 2025: 72.1% from 408 flights
- October 2025: 71.1% from 428 flights
- November 2025: 78.5% from 360 flights
- December 2025: 81.6% from 356 flights
- January 2026: 81.8% from 313 flights
- February 2026: 84.6% from 283 flights
- March 2026: 78.2% from 323 flights
- April 2026: 76.8% from 381 flights
- May 2026: 75.4% from 439 flights
- June 2026: 68.9% from 502 flights
- July 2026: 67.1% from 509 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 76.0% against 80.9% in the 12 months before — declining by 4.9 percentage points.
Data and methodology
Calculated by FlyerIntel from 14,227 SFO → BOS flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed