Route profile
BOS→SFO
Flight reliability, delays and best times to fly from Boston to San Francisco. · 2,704 miles
Right now
Current conditions at both ends of this route.
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Airport conditions describe the airfield, not any individual flight. An airport operating normally is not a guarantee that a specific flight will depart on time.
Route reliability
July 2023 – June 2026
Better than 39% of comparable major US routes (4,577 compared)
Calculated from 13,723 flights. How this is calculated
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – June 2026
Best time to fly
On-time arrival rate by scheduled local departure time.
BOS → SFO flights departing 5–9 AM arrived on time 83.5% of the time, against 58.0% for 9 PM–5 AM departures — a gap of 25.5 percentage points.
By departure window
By departure hour
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Buckets with fewer than 120 flights are not scored.
Why BOS → SFO runs late
Where US DOT attributed the delay minutes on this route.
airspace and airport capacity, including weather-driven flow control
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding, fuelling — 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 BOS → SFO. A single late flight can carry more than one cause, and only delays of fifteen minutes or more are attributed at all.
A route inherits the problems of both ends and of the aircraft flying it. A large share attributed to late-arriving aircraft usually means the departure sits late in a busy rotation rather than that anything about this city pair is difficult, which is why the same route often performs very differently at different times of day.
Airlines on this route
Performance by the carrier that actually operated the flight.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| United Airlines | 5,334 | 79.1% | 1.18% | -8 min | 7.6% |
| JetBlue | 4,846 | 72.4% | 0.70% | -6 min | 9.7% |
| Delta Air Lines | 2,425 | 73.7% | 0.91% | -6 min | 7.8% |
| Alaska Airlines | 1,117 | 69.2% | 1.16% | -3 min | 10.1% |
United Airlines arrived on time 9.9 percentage points more often than Alaska Airlines on this route.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Carriers with fewer than 200 flights on this route are not listed.
Individual flights on this route
The same route is not equally reliable at every hour. These are the flight numbers with enough operating history to judge separately.
| Flight | Scheduled | Operations | On time |
|---|---|---|---|
| B6333 JetBlue | 8:59 PM | 1,021 | 60.5% |
| UA2400 United Airlines | 6:18 PM | 1,006 | 62.9% |
| DL977 Delta Air Lines | 7:55 AM | 862 | 80.8% |
| B6733 JetBlue | 6:30 PM | 763 | 69.4% |
| B61833 JetBlue | 9:00 AM | 681 | 80.2% |
| B6133 JetBlue | 6:00 AM | 660 | 80.2% |
| B61333 JetBlue | 6:05 AM | 570 | 84.2% |
| UA2441 United Airlines | 6:00 AM | 553 | 86.0% |
| B62233 JetBlue | 11:00 AM | 440 | 69.4% |
| DL1655 Delta Air Lines | 5:00 PM | 414 | 67.6% |
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026 · Flight numbers with fewer than 270 operations on this route, or no longer scheduled, are not listed.
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Sunday the least, a gap of 8.9 percentage points.
By month
June is historically the weakest month and September the strongest, a spread of 13.5 percentage points.
Historical trend
On-time arrival rate by month.
Over the most recent 12 months (2025-07 to 2026-06), on-time arrivals averaged 72.6% against 79.1% in the 12 months before — declining by 6.5 percentage points.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – June 2026
Data and methodology
All figures on this page are calculated by FlyerIntel from 13,723 BOS → SFO flight records published by the US DOT Bureau of Transportation Statistics, covering July 2023 – June 2026. A flight is counted as delayed when it arrives 15 or more minutes after its scheduled arrival time, following BTS methodology. Cancelled and diverted flights have no arrival time and are excluded from on-time rates rather than counted as late.
Full methodology · Data sources · Report a problem
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