Boston to San Francisco Flight Delays
Sample size: 13,514 BOS–SFO flights, January 2023 to December 2025 (BTS). 23.29% of Boston to San Francisco flights arrived at least 15 minutes late. That tracks the 24.2% median for the major US domestic routes DelayGuard covers almost exactly. Departure time moves the odds more than anything else on this route: 06:00 departures run 15.09% late against 36.5% for 21:00. Tuesday is the calmest day at 18.89%, Sunday the worst at 26.59%. Cancellations (2024 to 2025) peak in January at 1.85% of scheduled flights and bottom out in September at 0%. Last updated: 2026-10-01.
These figures are historical US domestic rates, not a forecast for one departure. Use the delay risk check for your flight before you book.
BOS airport delay guide · SFO airport delay guide · Predict a BOS to SFO flight
Best time to fly BOS to SFO
The best time to fly BOS to SFO is the 6 AM departure and fly on a Tuesday, not a Sunday (18.89% against 26.59%): 15.09% of 6 AM flights arrived 15+ minutes late, against 36.5% at 9 PM.
Lowest observed delay rates depart 06:00, 08:00, 10:00. The highest sit at 19:00–21:00. 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 | 15.09% | 1,537 |
| 07:00 | 19.68% | 1,743 |
| 08:00 | 15.47% | 1,506 |
| 09:00 | 18.82% | 542 |
| 10:00 | 15.33% | 646 |
| 11:00 | 15.73% | 661 |
| 13:00 | 19.26% | 815 |
| 14:00 | 15.79% | 171 |
| 15:00 | 23.14% | 363 |
| 16:00 | 31.15% | 504 |
| 17:00 | 28.19% | 1,387 |
| 18:00 | 32.36% | 1,706 |
| 19:00 | 35.47% | 344 |
| 20:00 | 35.24% | 925 |
| 21:00 | 36.5% | 515 |
BOS to SFO flight time and distance
Scheduled gate-to-gate time from BOS to SFO is a median 6 h 45 min. Flights actually took a median 6 h 29 min gate to gate, including 6 h in the air. 3.0% ran 30 or more minutes over schedule and 74.6% arrived sooner than scheduled (BTS data, January 2023 to December 2025).
BOS to SFO is 2,704 miles (BTS data).
| Airline | Scheduled (median) | Actual (median) | In the air (median) | 30+ min over schedule | Flights |
|---|---|---|---|---|---|
| United Airlines | 6 h 40 min | 6 h 26 min | 5 h 58 min | 2.5% | 5,196 |
| JetBlue Airways | 6 h 45 min | 6 h 30 min | 6 h | 3.9% | 4,731 |
| Delta Air Lines | 6 h 52 min | 6 h 37 min | 6 h 5 min | 2.6% | 2,230 |
| Alaska Airlines | 6 h 45 min | 6 h 32 min | 5 h 57 min | 2.7% | 1,357 |
How late, and why
When a BOS to SFO flight was late (15+ minutes), it arrived an average of 65 minutes late (median 41). 8.2% of all completed flights arrived an hour or more late (BTS data, 2023 to 2025).
Of the delay minutes on late BOS to SFO flights, 34.2% were caused by the airline (crew, maintenance, ground handling), 33.7% by a late incoming aircraft, 29.0% by the air-traffic system (volume, non-extreme weather, airport operations), 3.0% by extreme weather and 0.1% by security (BTS data, 2023 to 2025).
| Cause | Share of delay minutes |
|---|---|
| airline | 34.2% |
| late incoming aircraft | 33.7% |
| air-traffic system | 29.0% |
| extreme weather | 3.0% |
| security | 0.1% |
BTS assigns causes to delay minutes on flights that arrived 15+ minutes late. "Air-traffic system" includes non-extreme weather that slows traffic.
BOS to SFO delays by day of week
| Day | Delayed 15+ min | Flights observed |
|---|---|---|
| Mon | 23.03% | 2,032 |
| Tue | 18.89% | 1,911 |
| Wed | 21.22% | 1,927 |
| Thu | 24.66% | 2,003 |
| Fri | 25% | 2,024 |
| Sat | 23.37% | 1,639 |
| Sun | 26.59% | 1,978 |
Month-by-month cancellation pattern
Share of scheduled BOS–SFO 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 | 1.85% | 593 |
| Feb | 1.29% | 543 |
| Mar | 0.15% | 652 |
| Apr | 0.14% | 694 |
| May | 0.24% | 829 |
| Jun | 0.6% | 832 |
| Jul | 1.79% | 893 |
| Aug | 0.58% | 858 |
| Sep | 0% | 815 |
| Oct | 0.35% | 855 |
| Nov | 1.24% | 723 |
| Dec | 0.68% | 734 |
Airlines on BOS to SFO: 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% | 19.4% | 0.76% | 3,407 |
| JetBlue Airways | 35% | 25.62% | 0.51% | 3,114 |
| Delta Air Lines | 18% | 24.26% | 0.73% | 1,643 |
| Alaska Airlines | 10% | 28.45% | 1.28% | 857 |
Related pages
- BOS delays: rate, worst hours and live risk
- SFO 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 BOS to SFO flight
Check your odds: Will my flight be delayed? · Will my flight be cancelled?
BOS vs SFO: airport conditions
Both ends of a route shape its delay profile. These are DelayGuard's operational scores for Boston and San Francisco.
| Measure | BOS (Boston) | SFO (San Francisco) |
|---|---|---|
| Congestion | high | high |
| Weather risk | moderate | moderate |
| NAS vulnerability | high | high |
| Average taxi-out | 16 min | 15 min |
| Runways | 6 | 4 |
BOS to SFO questions
- How long is the flight from Boston to San Francisco?
- Scheduled gate-to-gate time from BOS to SFO is a median 6 h 45 min, and flights actually took a median 6 h 29 min including 6 h in the air. 3.0% ran 30+ minutes over schedule (BTS data, January 2023 to December 2025).
- How often do BOS to SFO flights get delayed?
- Across 13,514 recorded BOS–SFO departures, January 2023 to December 2025 (BTS), 23.29% arrived at least 15 minutes late. Departure time matters most: 6:00 departures run 15.09% late against 36.5% for 21:00. Actual delay frequency varies by airline, time of day, and season.
- What is the best time of year to fly BOS to SFO?
- Boston (MA) sees its highest delays during December–February (winter weather) and June–August (summer storms). San Francisco (CA) peaks during November–February (coastal fog) with generally low risk year-round. The dominant seasonal risk on this route sits at the origin (Boston) — use the DelayGuard predictor to check conditions for your specific travel date.
- Which airline is most reliable on BOS to SFO?
- On BOS→SFO, United Airlines has the lowest measured delay rate at 19.4% of 5,196 flights, and Alaska Airlines the highest at 28.45% (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 BOS to SFO flights when they are delayed?
- When a BOS to SFO flight was late (15+ minutes), it arrived an average of 65 minutes late (median 41). 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.