Route reliability record

LAX→IAH

Los Angeles to Houston

Flights: 5,255
Period: July 2025 to June 2026
Distance: 1,379 mi
Carriers: 5

This route earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 7 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 5,255 flights, of which United Airlines flew 3,415 at 87.1% on time.

United Airlines is the most reliable of the four carriers covered here at 87.1% on time across 3,415 flights.

On time

84.6%

Arrivals under 15 minutes late, of 5,201 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

0.59%

National rate is 1.81%

Best carrier

United

87.1% on time across 3,415 flights

These figures cover 5,255 flights between July 2025 and June 2026. The median arrival is 7 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 LAX to IAH

The choice of carrier is not cosmetic here. United Airlines arrives on time 87.1% of the time; Spirit Airlines manages 77.5%. Sample sizes sit next to every figure, because a two-point gap across 455 flights means less than a ten-point one.

On-time performance by carrier on LAX to IAH
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	3,415	87.1%	55 min	0.26%	A+
Delta Air Lines	645	86.1%	73 min	1.09%	A
SkyWest Airlines	408	82.0%	68 min	0.49%	B+
Spirit Airlines	455	77.5%	83 min	1.32%	B
Frontier Airlinesthin sample	332	68.2%	71 min	2.11%	C

United leads Spirit by 10 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 16 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am746 flights93.7%
8am–11am1,240 flights88.1%
11am–2pm1,074 flights78.0%
2pm–5pm657 flights77.9%
5pm–8pm840 flights81.4%
8pm–5am698 flights88.8%

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 93.7% of the time, against 77.9% for the afternoon window. That is 16 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 1,240 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 15 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.

Darker means more delays. Figures are on-time percentages.September best, November worst

September is the best month on the calendar at 92.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. October was the busiest month here, with 493 flights.

Across the week, Thursday is the strongest day at 87.5% on time and Saturday the weakest at 82.3%. 5 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 51,000 reported delay minutes.

Late-arriving aircraft
36%
Carrier
35%
National Airspace System
28%
Extreme weather
1%

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 51,000 reported delay minutes here, that single category outweighs weather by 26 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 51,291 reported delay minutes.

The largest share of delay minutes, 35%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 18,000 of the 51,000 delay minutes reported here.

Cancellations are rare at 0.59%, 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 actually costs

5.2% 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 about an hour kind, which a normal layover absorbs.

The 1,379 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 83.6% on time across 5,260 flights, within about a point 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 5,255 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. September runs 92.3% on time and November 77.4%, a swing of 15 points. If the dates move at all, move them out of November before you think about anything else. 5,201 completed flights over 12 months sit behind that.

Common questions

LAX to IAH questions

How often is LAX to IAH delayed?

Roughly 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 15.4% of the 5,255 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on LAX to IAH?

United Airlines leads at 87.1% on time across 3,415 flights. Spirit Airlines is at the other end on 77.5%, a gap of 10 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 LAX to IAH?

The 5am–8am departure window is the strongest at 93.7% on time. The 2pm–5pm window is the weakest at 77.9%, 16 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 November delays on LAX to IAH?

November is the weakest month at 77.4% on time, compared with 92.3% in September. Across the year that is 15 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. LAX to IAH and IAH to LAX 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.

Key figures