Carrier route record

UABOS→LAX

United Airlines · Boston to Los Angeles

Flights: 716
Period: July 2025 to June 2026
Share of route: 15%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.

United on BOS to LAX lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 716 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,228 at 75.2% on time.

The US average over the same twelve months is 77.6%, so there is little to separate United on BOS to LAX from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

76.8%

Arrivals under 15 minutes late, of 706 completed flights

Avg delay

67 min

Across delayed arrivals only, not all flights

Cancelled

1.12%

National rate is 1.81%

Whole route

74.9%

Every carrier on BOS to LAX, 4,713 flights

These figures cover 716 flights between July 2025 and June 2026. The median arrival is 4 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

United against every carrier on BOS to LAX

United flew 716 of the 4,713 flights on BOS to LAX, about 15% of it. Its 76.8% on time is 2 points better than the route as a whole, which runs 74.9%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from United at 76.8% to American at 74.0%.

The three carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on BOS to LAX
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)	716	76.8%	67 min	1.12%	B
Delta Air Lines	1,228	75.2%	76 min	1.71%	B
JetBlue Airways	1,626	74.5%	71 min	1.41%	C
American Airlines	1,143	74.0%	91 min	1.31%	C

No carrier stands out. Delta tops the table at 75.2%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.

Departure window

When United runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 26 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am191 flights91.6%
8am–11am177 flights80.2%
11am–2pm10 flights—
2pm–5pm—
5pm–8pm338 flights65.8%
8pm–5am—

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 91.6% of the time, against 65.8% for the evening window. That is 26 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 338 flights scheduled in it.

Across the year

United on BOS to LAX through the year

Darker means more delays. Figures are on-time percentages.March best, December worst

December is the weak month at 67.7% on time, against 84.7% in March. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. December was the busiest month here, with 63 flights.

Across the week, Tuesday is the strongest day at 89.0% on time and Thursday the weakest at 69.2%. 20 points is a smaller lever than departure hour, but it is free.

Delay causes

Why United runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 54% of the 11,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Late-arriving aircraft
54%
Carrier
25%
National Airspace System
19%
Extreme weather
2%

54% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 11,000 reported delay minutes here, that single category outweighs weather by 28 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 10,957 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 91.6% on time here.

Cancellations sit at 1.12% against a national 1.81%, which is ordinary. Diversions add another 0.28%.

Connections and stage length

What a delay here costs

7.6% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

At 2,611 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.

The return leg is a different operation and performs like one: it runs 87.0% on time across 716 flights, 10 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 10 points of difference.

One caution: this is a thin sample. 716 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking United on BOS to LAX

Put together: treat all of this as provisional. 716 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 76.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 706 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures