Route reliability record

IAH→DTW

Houston to Detroit

Flights: 2,137
Period: July 2025 to June 2026
Distance: 1,075 mi
Carriers: 5

This route lands a B, about a point better than the national rate of 77.6%. About one flight in five 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 2,137 flights, of which Delta Air Lines flew 1,322 at 82.3% on time.

The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

78.8%

Arrivals under 15 minutes late, of 2,104 completed flights

Avg delay

73 min

Across delayed arrivals only, not all flights

Cancelled

1.22%

National rate is 1.81%

Best carrier

Delta

82.3% on time across 1,322 flights

These figures cover 2,137 flights between July 2025 and June 2026. The median arrival is 6 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 DTW

The two carriers here are closely matched: 6 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on IAH to DTW
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlinesthin sample	3	100.0%	—	0.00%	A+
Delta Air Lines	1,322	82.3%	76 min	0.76%	B+
Spirit Airlines	408	76.4%	88 min	2.45%	B
United Airlinesthin sample	283	70.3%	58 min	1.41%	C
Frontier Airlinesthin sample	121	68.6%	54 min	1.65%	C

No carrier stands out. Delta tops the table at 82.3%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.

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 20 points, against 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am546 flights88.3%
8am–11am32 flights—
11am–2pm375 flights81.8%
2pm–5pm527 flights78.8%
5pm–8pm327 flights70.1%
8pm–5am330 flights68.8%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 88.3% of the time, against 68.8% for the overnight 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 5am–8am window is the busiest, with 546 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 21 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, March worst

September is the best month on the calendar at 89.4% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. August was the busiest month here, with 206 flights.

Across the week, Wednesday is the strongest day at 84.1% on time and Saturday the weakest at 76.0%. 8 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

One category carries most of the weight here. Carrier accounts for 46% of the 32,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Carrier
46%
Late-arriving aircraft
33%
National Airspace System
15%
Extreme weather
5%
Security
0%

The largest share of delay minutes, 46%, 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 15,000 of the 32,000 delay minutes reported here. The split is drawn from 32,437 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 88.3% on time here.

Cancellations sit at 1.22% against a national 1.81%, which is ordinary. Diversions add another 0.33%.

Connections and stage length

What a delay here actually costs

6.7% 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 1,075 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 79.7% on time across 2,129 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 2,137 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 89.4% on time and March 68.8%, a swing of 21 points. If the dates move at all, move them out of March before you think about anything else. 2,104 completed flights over 12 months sit behind that.

Common questions

IAH to DTW questions

How often is IAH to DTW delayed?

About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.2% of the 2,137 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 IAH to DTW?

Delta Air Lines leads at 82.3% on time across 1,322 flights. Spirit Airlines is at the other end on 76.4%, a gap of 6 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 DTW?

The 5am–8am departure window is the strongest at 88.3% on time. The 8pm–5am window is the weakest at 68.8%, 20 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 IAH to DTW?

March is the weakest month at 68.8% on time, compared with 89.4% in September. Across the year that is 21 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 DTW and DTW 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