About 1 in 3 UA 639 flights from Boston arrived 15+ minutes late, diverted or cancelled over the past year (36%); 0.0% were cancelled. The typical flight landed 2 minutes late.
UA 639: BOS → LAX
Scheduled to leave Boston at 6:26 p.m. local time. Over the past year it arrived on time 64% of the time (143 flights), in line with other UA flights on the route at that hour (64%). Last seen in the data Aug 10, 2026.
Usually United Airlines's last flight of the day from Boston to Los Angeles (100% of days). United Airlines's last BOS–LAX flight was cancelled 0.9% of the time, against 1.1% for its earlier ones. If it's cancelled, the next United Airlines flight is usually around 6:21 a.m. the next morning.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 23 | 65% |
| Tuesday | 14 | — |
| Wednesday | 19 | — |
| Thursday | 23 | 52% |
| Friday | 23 | 61% |
| Saturday | 18 | — |
| Sunday | 23 | 52% |
Why it was late
All flights BOS → LAX · Connecting off UA 639? Check the risk
Questions
How often is UA 639 from BOS to LAX late?
United Airlines 639 from Boston, MA to Los Angeles, CA arrived 15 or more minutes late, was diverted or was cancelled on 36% of 143 scheduled flights between September 2025 and August 2026. 0.0% were cancelled.
Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check United Airlines for today's flight. Method.