Route reliability record
LAS→IAH
Las Vegas to Houston
- Flights
- 3,455
- Period
- July 2025 to June 2026
- Distance
- 1,222 mi
- Carriers
- 3
This route lands a B+, 6 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 3,455 flights, of which United Airlines flew 2,601 at 85.6% on time.
Set against the rest of the country, this route's 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.
Key figures
On time
83.9%
Arrivals under 15 minutes late, of 3,410 completed flights
Avg delay
75 min
Across delayed arrivals only, not all flights
Cancelled
0.93%
National rate is 1.81%
Best carrier
United
85.6% on time across 2,601 flights
These figures cover 3,455 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
Which airline is most reliable on LAS to IAH
The choice of carrier is not cosmetic here. United Airlines arrives on time 85.6% of the time; Spirit Airlines manages 77.6%. Sample sizes sit next to every figure, because a two-point gap across 526 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 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 |
United leads Spirit by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 19 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am411 flights94.3%
- 8am–11am941 flights88.0%
- 11am–2pm624 flights77.7%
- 2pm–5pm632 flights74.9%
- 5pm–8pm247 flights79.5%
- 8pm–5am600 flights88.1%
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 94.3% of the time, against 74.9% for the afternoon window. That is 19 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 941 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 14 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
Delays peak in March, when the on-time rate falls to 77.7%. December is the strongest month at 91.6%. Moving a flexible trip across that boundary buys 14 points. March was the busiest month here, with 323 flights.
Across the week, Wednesday is the strongest day at 88.9% on time and Friday the weakest at 80.4%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
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 41,000 reported delay minutes.
- 36%Late-arriving aircraft
- 33%Carrier
- 28%National Airspace System
- 3%Extreme weather
36% 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 41,000 reported delay minutes here, that single category outweighs weather by 11 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 41,425 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 94.3% on time here.
Cancellations sit at 0.93% against a national 1.81%, which is ordinary. Diversions add another 0.38%.
Connections and stage length
What a delay here actually 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 are the a little over an hour kind, 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 82.4% on time across 3,457 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 3,455 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. December runs 91.6% on time and March 77.7%, a swing of 14 points. If the dates move at all, move them out of March before you think about anything else. 3,410 completed flights over 12 months sit behind that.
Common questions
LAS to IAH questions
How often is LAS to IAH delayed?
About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.1% of the 3,455 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on LAS to IAH?
United Airlines leads at 85.6% on time across 2,601 flights. Spirit Airlines is at the other end on 77.6%, a gap of 8 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on LAS to IAH?
The 5am–8am departure window is the strongest at 94.3% on time. The 2pm–5pm window is the weakest at 74.9%, 19 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are March delays on LAS to IAH?
March is the weakest month at 77.7% on time, compared with 91.6% in December. Across the year that is 14 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- IAH to LAS — the return legseparate record
- Harry Reid International (LAS) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- United Airlines on-time record85.6%
- Frontier Airlines on-time record80.2%
- Spirit Airlines on-time record77.6%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. LAS to IAH and IAH to LAS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.