San Francisco to Boston Flight Delays
Sample size: 13,521 SFO–BOS flights, January 2023 to December 2025 (BTS). 22.01% of San Francisco to Boston flights arrived at least 15 minutes late. That is 2.2 points better than the 24.2% median for those routes, making this one of the steadier pairings in the network. Departure time moves the odds more than anything else on this route: 06:00 departures run 11.17% late against 30.03% for 10:00. Saturday is the calmest day at 17.55%, Sunday the worst at 25.57%. Cancellations (2024 to 2025) peak in January at 2.03% of scheduled flights and bottom out in September at 0.12%. Last updated: 2026-10-01.
These figures are historical US domestic rates, not a forecast for one departure. Use the per-flight delay estimate before you book.
SFO airport delay guide · BOS airport delay guide · Predict a SFO to BOS flight
Best time to fly SFO to BOS
The best time to fly SFO to BOS is the 6 AM departure and fly on a Saturday, not a Sunday (17.55% against 25.57%): 11.17% of 6 AM flights arrived 15+ minutes late, against 30.03% at 10 AM.
Lowest observed delay rates depart 06:00–07:00, 16:00. The highest sit at 09:00–11:00. Only departure hours with at least 100 recorded flights are listed, so sparse hours are blank rather than estimated.
| Departure hour | Delayed 15+ min | Flights observed |
|---|---|---|
| 06:00 | 11.17% | 573 |
| 07:00 | 12.48% | 1,707 |
| 08:00 | 17.53% | 1,369 |
| 09:00 | 29.2% | 250 |
| 10:00 | 30.03% | 776 |
| 11:00 | 29.52% | 1,067 |
| 12:00 | 26.51% | 777 |
| 13:00 | 25.91% | 1,559 |
| 14:00 | 23.66% | 596 |
| 15:00 | 22.22% | 774 |
| 16:00 | 16.85% | 184 |
| 20:00 | 19.61% | 622 |
| 21:00 | 23.1% | 1,104 |
| 22:00 | 27.71% | 664 |
| 23:00 | 21.63% | 1,493 |
SFO to BOS flight time and distance
Scheduled gate-to-gate time from SFO to BOS is a median 5 h 42 min. Flights actually took a median 5 h 34 min gate to gate, including 5 h 5 min in the air. 2.3% ran 30 or more minutes over schedule and 69.4% arrived sooner than scheduled (BTS data, January 2023 to December 2025).
SFO to BOS is 2,704 miles (BTS data).
| Airline | Scheduled (median) | Actual (median) | In the air (median) | 30+ min over schedule | Flights |
|---|---|---|---|---|---|
| United Airlines | 5 h 43 min | 5 h 33 min | 5 h 4 min | 1.8% | 5,206 |
| JetBlue Airways | 5 h 39 min | 5 h 33 min | 5 h 6 min | 3.0% | 4,725 |
| Delta Air Lines | 5 h 44 min | 5 h 34 min | 5 h 4 min | 1.8% | 2,224 |
| Alaska Airlines | 5 h 42 min | 5 h 36 min | 5 h 7 min | 2.9% | 1,366 |
How late, and why
When a SFO to BOS flight was late (15+ minutes), it arrived an average of 69 minutes late (median 42). 8.2% of all completed flights arrived an hour or more late (BTS data, 2023 to 2025).
Of the delay minutes on late SFO to BOS flights, 35.3% were caused by a late incoming aircraft, 32.4% by the air-traffic system (volume, non-extreme weather, airport operations), 30.6% by the airline (crew, maintenance, ground handling), 1.7% by extreme weather and 0.0% by security (BTS data, 2023 to 2025).
| Cause | Share of delay minutes |
|---|---|
| late incoming aircraft | 35.3% |
| air-traffic system | 32.4% |
| airline | 30.6% |
| extreme weather | 1.7% |
| security | 0.0% |
BTS assigns causes to delay minutes on flights that arrived 15+ minutes late. "Air-traffic system" includes non-extreme weather that slows traffic.
SFO to BOS delays by day of week
| Day | Delayed 15+ min | Flights observed |
|---|---|---|
| Mon | 23.29% | 2,014 |
| Tue | 17.64% | 1,910 |
| Wed | 19.48% | 1,940 |
| Thu | 25.41% | 2,019 |
| Fri | 23.85% | 2,029 |
| Sat | 17.55% | 1,595 |
| Sun | 25.57% | 2,014 |
Month-by-month cancellation pattern
Share of scheduled SFO–BOS flights cancelled in each month, from BTS 2024–2025 on-time reporting. These are cancellations, not delays. Delay figures on this page cover January 2023 to December 2025.
| Month | Cancelled | Flights scheduled |
|---|---|---|
| Jan | 2.03% | 592 |
| Feb | 1.1% | 545 |
| Mar | 0.15% | 653 |
| Apr | 0.14% | 692 |
| May | 0.24% | 831 |
| Jun | 0.24% | 833 |
| Jul | 1.68% | 893 |
| Aug | 0.58% | 856 |
| Sep | 0.12% | 815 |
| Oct | 0.35% | 855 |
| Nov | 1.39% | 722 |
| Dec | 0.55% | 731 |
Airlines on SFO to BOS: delays and cancellations
United Airlines, JetBlue Airways, Delta Air Lines and Alaska Airlines fly this route today. Only carriers with at least 200 scheduled flights on the pairing are listed. Delay rates cover January 2023 to December 2025; cancellation rates cover 2024 to 2025.
| Airline | Share of flights | Delayed 15+ min | Cancelled | Flights scheduled |
|---|---|---|---|---|
| United Airlines | 38% | 21.59% | 0.56% | 3,408 |
| JetBlue Airways | 34% | 22.52% | 0.51% | 3,109 |
| Delta Air Lines | 18% | 22.3% | 0.91% | 1,643 |
| Alaska Airlines | 10% | 21.38% | 1.4% | 858 |
Related pages
- SFO delays: rate, worst hours and live risk
- BOS delays: rate, worst hours and live risk
- Boston to DC flights (BOS to DCA)
- DC to Boston flights (DCA to BOS)
- US airline cancellation rates
- Thanksgiving and Christmas 2026 flight delay guide
- Predict a SFO to BOS flight
Check your odds: Will my flight be delayed? · Will my flight be cancelled?
SFO vs BOS: airport conditions
Both ends of a route shape its delay profile. These are DelayGuard's operational scores for San Francisco and Boston.
| Measure | SFO (San Francisco) | BOS (Boston) |
|---|---|---|
| Congestion | high | high |
| Weather risk | moderate | moderate |
| NAS vulnerability | high | high |
| Average taxi-out | 15 min | 16 min |
| Runways | 4 | 6 |
SFO to BOS questions
- How long is the flight from San Francisco to Boston?
- Scheduled gate-to-gate time from SFO to BOS is a median 5 h 42 min, and flights actually took a median 5 h 34 min including 5 h 5 min in the air. 2.3% ran 30+ minutes over schedule (BTS data, January 2023 to December 2025).
- How often do SFO to BOS flights get delayed?
- Across 13,521 recorded SFO–BOS departures, January 2023 to December 2025 (BTS), 22.01% arrived at least 15 minutes late. Departure time matters most: 6:00 departures run 11.17% late against 30.03% for 10:00. Actual delay frequency varies by airline, time of day, and season.
- What is the best time of year to fly SFO to BOS?
- San Francisco (CA) sees its highest delays during November–February (coastal fog) with generally low risk year-round. Boston (MA) peaks during December–February (winter weather) and June–August (summer storms). The dominant seasonal risk on this route sits at the destination (Boston) — use the DelayGuard predictor to check conditions for your specific travel date.
- Which airline is most reliable on SFO to BOS?
- On SFO→BOS, Alaska Airlines has the lowest measured delay rate at 21.38% of 1,366 flights, and JetBlue Airways the highest at 22.52% (BTS, January 2023 to December 2025). JetBlue Airways cancels the fewest at 0.51% (2024 to 2025). These are route-specific figures, not airline-wide averages.
- How late are SFO to BOS flights when they are delayed?
- When a SFO to BOS flight was late (15+ minutes), it arrived an average of 69 minutes late (median 42). 8.2% of all completed flights arrived an hour or more late (BTS data, 2023 to 2025).
- How accurate is DelayGuard's delay prediction for this route?
- DelayGuard's delay risk score comes from an ML model trained on BTS data (3.95 million US domestic flights, 2023 to mid-2025), with live weather data (within 5 days of departure) and FAA NAS advisories (within 6 hours) — a likelihood of delay, not a guarantee.
Delay figures reflect arrivals 15 or more minutes late in BTS on-time reporting. Cancellation figures are separate and count flights that never operated. Hours, days and months with fewer than 100 recorded flights are omitted rather than estimated.