Route reliability record

DTW→IAH

Detroit to Houston

Flights: 2,129
Period: July 2025 to June 2026
Distance: 1,075 mi
Carriers: 5

This route lands a B, 2 points 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 about an hour on average. That is a workable record, not a spotless one. That rests on 2,129 flights, of which Delta Air Lines flew 1,322 at 79.8% 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

79.7%

Arrivals under 15 minutes late, of 2,103 completed flights

Avg delay

63 min

Across delayed arrivals only, not all flights

Cancelled

1.08%

National rate is 1.81%

Best carrier

Delta

79.8% on time across 1,322 flights

These figures cover 2,129 flights between July 2025 and June 2026. The median arrival is 8 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 DTW to IAH

The two carriers here are closely matched: about a point 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 DTW to IAH
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlinesthin sample	281	87.0%	53 min	1.42%	A
Delta Air Lines	1,322	79.8%	55 min	0.83%	B+
Spirit Airlines	403	78.5%	85 min	1.74%	B
SkyWest Airlinesthin sample	3	66.7%	19 min	0.00%	C+
Frontier Airlinesthin sample	120	65.5%	73 min	0.83%	C+

No carrier stands out. Delta tops the table at 79.8%, about a point 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 15 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am191 flights85.2%
8am–11am702 flights84.1%
11am–2pm354 flights86.0%
2pm–5pm341 flights70.6%
5pm–8pm106 flights77.4%
8pm–5am435 flights72.5%

Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.

The best window here is not the first bank but the 11am–2pm slot at 86.0% on time, ahead of 2pm–5pm at 70.6%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 8am–11am window is the busiest, with 702 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 33 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, December worst

December is the weak month at 61.4% on time, against 94.5% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. March was the busiest month here, with 203 flights.

Across the week, Tuesday is the strongest day at 82.6% on time and Saturday the weakest at 75.6%. 7 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 43% of the 27,000 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
43%
National Airspace System
33%
Late-arriving aircraft
21%
Extreme weather
2%
Security
0%

The largest share of delay minutes, 43%, 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 12,000 of the 27,000 delay minutes reported here. The split is drawn from 26,809 reported delay minutes.

33% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 8,882 minutes out of 27,000, against a national NAS share of 21%.

Cancellations sit at 1.08% against a national 1.81%, which is ordinary. Diversions add another 0.14%.

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 about 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 78.8% on time across 2,137 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 2,129 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 94.5% on time and December 61.4%, a swing of 33 points. If the dates move at all, move them out of December before you think about anything else. 2,103 completed flights over 12 months sit behind that.

Common questions

DTW to IAH questions

How often is DTW to IAH 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 20.3% of the 2,129 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on DTW to IAH?

Delta Air Lines leads at 79.8% on time across 1,322 flights. Spirit Airlines is at the other end on 78.5%, a gap of about a point. 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 DTW to IAH?

The 11am–2pm departure window is the strongest at 86.0% on time. The 2pm–5pm window is the weakest at 70.6%, 15 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 December delays on DTW to IAH?

December is the weakest month at 61.4% on time, compared with 94.5% in September. Across the year that is 33 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. DTW to IAH and IAH to DTW 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