Route reliability record

IAH→LAX

Houston to Los Angeles

Flights: 5,260
Period: July 2025 to June 2026
Distance: 1,379 mi
Carriers: 6

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 about an hour on average. That is a workable record, not a spotless one. That rests on 5,260 flights, of which Delta Air Lines flew 645 at 88.5% on time.

Delta Air Lines is the most reliable of the four carriers covered here at 88.5% on time across 645 flights.

On time

83.6%

Arrivals under 15 minutes late, of 5,223 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

0.57%

National rate is 1.81%

Best carrier

Delta

88.5% on time across 645 flights

These figures cover 5,260 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

Which airline is most reliable on IAH to LAX

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 88.5% of the time; SkyWest Airlines manages 78.3%. Sample sizes sit next to every figure, because a two-point gap across 408 flights means less than a ten-point one.

On-time performance by carrier on IAH to LAX
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlinesthin sample	1	100.0%	—	0.00%	A+
Delta Air Lines	645	88.5%	86 min	1.09%	A
United Airlines	3,416	84.4%	59 min	0.32%	B+
Spirit Airlines	458	83.6%	70 min	1.31%	B
SkyWest Airlines	408	78.3%	75 min	0.49%	B+
Frontier Airlinesthin sample	332	72.6%	60 min	1.20%	C

Delta leads SkyWest 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 17 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,266 flights93.7%
8am–11am428 flights85.4%
11am–2pm492 flights83.6%
2pm–5pm1,249 flights82.2%
5pm–8pm673 flights76.6%
8pm–5am1,152 flights77.3%

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 76.6% for the evening 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 5am–8am window is the busiest, with 1,266 flights scheduled in it.

Across the year

When delays peak on this route

Twelve months, one bar each, drawn from the same 5,260 flights. The strip shows how much of this route's record is set by the calendar rather than by the operation.

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

July is the worst month at 78.2% on time, 8 points below September, the best at 86.6%. 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. October was the busiest month here, with 493 flights.

Across the week, Wednesday is the strongest day at 88.1% on time and Saturday the weakest at 80.1%. 8 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 55,000 reported delay minutes.

Carrier
41%
Late-arriving aircraft
34%
National Airspace System
17%
Extreme weather
8%
Security
0%

34% 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 55,000 reported delay minutes here, that single category outweighs weather by 4 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 54,689 reported delay minutes.

The largest share of delay minutes, 41%, 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 22,000 of the 55,000 delay minutes reported here.

Cancellations are rare at 0.57%, 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 84.6% on time across 5,255 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 5,260 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: avoid the 5pm–8pm departure. It runs 76.6% on time against 93.7% for the 5am–8am slot, and that 17 points is the largest single thing you control here. Delta Air Lines is the strongest operator if the fares are close. 5,223 completed flights over 12 months sit behind that.

Common questions

IAH to LAX questions

How often is IAH to LAX 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 16.4% of the 5,260 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on IAH to LAX?

Delta Air Lines leads at 88.5% on time across 645 flights. SkyWest Airlines is at the other end on 78.3%, 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 IAH to LAX?

The 5am–8am departure window is the strongest at 93.7% on time. The 5pm–8pm window is the weakest at 76.6%, 17 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 July delays on IAH to LAX?

July is the weakest month at 78.2% on time, compared with 86.6% in September. Across the year that is 8 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. IAH to LAX and LAX to IAH 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