Carrier route record

UAIAH→LAS

United Airlines · Houston to Las Vegas

Flights: 2,602
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 IAH to LAS lands a B+, 6 points better than the national rate of 77.6%. About one flight in six 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 2,602 flights, with a median arrival 10 minutes early.

Set against the rest of the country, United's IAH to LAS record is 6 points better than the US average of 77.6%. That gap is worth roughly 63 fewer late arrivals for every thousand flights.

On time

83.9%

Arrivals under 15 minutes late, of 2,591 completed flights

Avg delay

59 min

Across delayed arrivals only, not all flights

Cancelled

0.38%

National rate is 1.81%

Whole route

82.4%

Every carrier on IAH to LAS, 3,457 flights

These figures cover 2,602 flights between July 2025 and June 2026. The median arrival is 10 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 IAH to LAS

United flew 2,602 of the 3,457 flights on IAH to LAS, most of the route. Its 83.9% on time is 2 points better than the route as a whole, which runs 82.4%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 83.9% to Frontier at 71.7%. 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 IAH to LAS
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)	2,602	83.9%	59 min	0.38%	B+
Spirit Airlines	527	81.9%	78 min	2.09%	B
Frontier Airlinesthin sample	328	71.7%	126 min	2.13%	C

Flight by flight

United flight numbers on IAH to LAS

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 17 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–8am314 flights94.6%
8am–11am345 flights89.8%
11am–2pm404 flights86.1%
2pm–5pm645 flights82.4%
5pm–8pm465 flights78.0%
8pm–5am429 flights77.6%

Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 94.6% of the time, against 77.6% for the overnight window. That is 17 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 645 flights scheduled in it.

Across the year

United on IAH to LAS through the year

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

July is the worst month at 72.6% on time, 22 points below December, the best at 94.1%. 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 89.3% on time and Friday the weakest at 78.4%. 11 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 25,000 reported delay minutes.

Late-arriving aircraft
38%
Carrier
28%
National Airspace System
27%
Extreme weather
7%

38% 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 25,000 reported delay minutes here, that single category outweighs weather by 5 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 24,666 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 94.6% on time here.

Cancellations are rare at 0.38%, 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

5.4% 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.

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 85.6% on time across 2,601 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 2,602 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 IAH to LAS

Put together: the calendar is the biggest lever here, not the carrier or the hour. December runs 94.1% on time and July 72.6%, a swing of 22 points. If the dates move at all, move them out of July before you think about anything else. 2,591 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