Carrier route record

UALAS→IAH

United Airlines · Las Vegas to Houston

Flights: 2,601
Period: July 2025 to June 2026
Share of route: 75%
Carriers: 3

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

United on LAS to IAH earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 2,601 flights, with a median arrival 9 minutes early.

Set against the rest of the country, United's LAS to IAH record is 8 points better than the US average of 77.6%. That gap is worth roughly 80 fewer late arrivals for every thousand flights.

On time

85.6%

Arrivals under 15 minutes late, of 2,573 completed flights

Avg delay

73 min

Across delayed arrivals only, not all flights

Cancelled

0.58%

National rate is 1.81%

Whole route

83.9%

Every carrier on LAS to IAH, 3,455 flights

These figures cover 2,601 flights between July 2025 and June 2026. The median arrival is 9 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 LAS to IAH

United flew 2,601 of the 3,455 flights on LAS to IAH, most of the route. Its 85.6% on time is 2 points better than the route as a whole, which runs 83.9%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 85.6% to Spirit at 77.6%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on LAS to IAH
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)	2,601	85.6%	73 min	0.58%	A+
Frontier Airlinesthin sample	328	80.2%	60 min	1.22%	B
Spirit Airlines	526	77.6%	92 min	2.47%	B

Flight by flight

United flight numbers on LAS to IAH

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 20 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am326 flights95.9%
8am–11am726 flights90.1%
11am–2pm488 flights77.5%
2pm–5pm500 flights75.5%
5pm–8pm197 flights83.0%
8pm–5am364 flights93.6%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 95.9% of the time, against 75.5% for the afternoon window. That is 20 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 726 flights scheduled in it.

Across the year

United on LAS to IAH through the year

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

July is the worst month at 80.1% on time, 13 points below December, the best at 92.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. March was the busiest month here, with 253 flights.

Across the week, Wednesday is the strongest day at 89.0% on time and Friday the weakest at 81.6%. 7 points is a smaller lever than departure hour, but it is free.

Delay causes

Why United runs late on this route

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 27,000 reported delay minutes.

Late-arriving aircraft
40%
National Airspace System
28%
Carrier
27%
Extreme weather
4%

40% 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 27,000 reported delay minutes here, that single category outweighs weather by 9 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 26,961 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 95.9% on time here.

Cancellations are rare at 0.58%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 4.7% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

The 1,222 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg runs 83.9% on time across 2,602 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

The sample behind these figures is 2,601 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking United on LAS to IAH

Put together: the calendar is the biggest lever here, not the carrier or the hour. December runs 92.9% on time and July 80.1%, a swing of 13 points. If the dates move at all, move them out of July before you think about anything else. 2,573 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