Carrier route record

NKDTW→IAH

Spirit Airlines · Detroit to Houston

Flights: 403
Period: July 2025 to June 2026
Share of route: 19%
Carriers: 5

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Spirit Airlines.

Spirit on DTW to IAH lands a B, about a point better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 403 flights, with a median arrival 10 minutes early.

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

On time

78.5%

Arrivals under 15 minutes late, of 396 completed flights

Avg delay

85 min

Across delayed arrivals only, not all flights

Cancelled

1.74%

National rate is 1.81%

Whole route

79.7%

Every carrier on DTW to IAH, 2,129 flights

These figures cover 403 flights between July 2025 and June 2026. Beyond the headline rate, 8.8% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Carrier by carrier

Spirit against every carrier on DTW to IAH

Spirit flew 403 of the 2,129 flights on DTW to IAH, about 19% of it. Its 78.5% on time is about level with the route as a whole at 79.7%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from United at 87.0% to Frontier at 65.5%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

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 (this page)	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+

Departure window

When Spirit runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 28 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am86 flights89.4%
8am–11am92 flights78.0%
11am–2pm28 flights—
2pm–5pm5 flights—
5pm–8pm97 flights82.5%
8pm–5am95 flights61.5%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 61.5% on time, against 89.4% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5pm–8pm window is the busiest, with 97 flights scheduled in it.

Across the year

Spirit on DTW to IAH through the year

Jul–Sep 2025160 flights89.4%
Oct–Dec 2025130 flights78.1%
Jan–Mar 202685 flights67.1%
Apr–Jun 202628 flights—

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

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 78.5% on time across 403 flights.

Spirit on DTW to IAH did not run the same all year. Its best quarter was Jul–Sep 2025 at 89.4% on time and its weakest Jan–Mar 2026 at 67.1%, a swing of 22 points on roughly 134 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Tuesday is the strongest day at 88.0% on time and Friday the weakest at 71.0%. 17 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Spirit runs late on this route

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 7,259 reported delay minutes.

National Airspace System
41%
Carrier
37%
Late-arriving aircraft
21%
Extreme weather
1%
Security
0%

The largest share of delay minutes, 37%, 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 2,676 of the 7,259 delay minutes reported here. The split is drawn from 7,259 reported delay minutes.

41% 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 3,010 minutes out of 7,259, against a national NAS share of 21%.

Cancellations sit at 1.74% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and stage length

What a delay here costs

8.8% 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 last an hour and a half, 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 76.4% on time across 408 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.

One caution: this is a thin sample. 403 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Spirit on DTW to IAH

Put together: treat all of this as provisional. 403 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 78.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 396 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures