Carrier route record

NKIAH→DTW

Spirit Airlines · Houston to Detroit

Flights: 408
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 IAH to DTW lands a B, about a point worse than the national rate of 77.6%. About one flight in four 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 408 flights, with a median arrival 2 minutes early.

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

On time

76.4%

Arrivals under 15 minutes late, of 398 completed flights

Avg delay

88 min

Across delayed arrivals only, not all flights

Cancelled

2.45%

National rate is 1.81%

Whole route

78.8%

Every carrier on IAH to DTW, 2,137 flights

These figures cover 408 flights between July 2025 and June 2026. The median arrival is 2 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

Spirit against every carrier on IAH to DTW

Spirit flew 408 of the 2,137 flights on IAH to DTW, about 19% of it. Its 76.4% on time is 2 points worse than the route as a whole, which runs 78.8%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from SkyWest at 100.0% to Frontier at 68.6%. 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 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 (this page)	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

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 18 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–8am150 flights84.2%
8am–11am26 flights—
11am–2pm1 flights—
2pm–5pm110 flights73.6%
5pm–8pm30 flights—
8pm–5am91 flights66.3%

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

Book the early departure. Flights leaving between 5am–8am arrive on time 84.2% of the time, against 66.3% for the overnight window. That is 18 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 150 flights scheduled in it.

Across the year

Spirit on IAH to DTW through the year

Jul–Sep 2025162 flights82.7%
Oct–Dec 2025130 flights77.3%
Jan–Mar 202687 flights70.0%
Apr–Jun 202629 flights—

Scale runs 60% to 90%. 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 76.4% on time across 408 flights.

Spirit on IAH to DTW did not run the same all year. Its best quarter was Jul–Sep 2025 at 82.7% on time and its weakest Jan–Mar 2026 at 70.0%, a swing of 13 points on roughly 136 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, Wednesday is the strongest day at 81.5% on time and Saturday the weakest at 65.2%. 16 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Spirit runs late on this route

One category carries most of the weight here. Carrier accounts for 56% of the 8,236 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
56%
National Airspace System
18%
Extreme weather
14%
Late-arriving aircraft
12%
Security
0%

Extreme weather accounts for 14% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.2 times the usual weather exposure. The split is drawn from 8,236 reported delay minutes.

The largest share of delay minutes, 56%, 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 4,626 of the 8,236 delay minutes reported here.

Cancellations sit at 2.45% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and stage length

What a delay here costs

6.8% 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 78.5% on time across 403 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. 408 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 IAH to DTW

Put together: treat all of this as provisional. 408 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 76.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 398 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