Carrier route record

NKIAH→ATL

Spirit Airlines · Houston to Atlanta

Flights: 375
Period: July 2025 to June 2026
Share of route: 8%
Carriers: 4

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

Spirit on IAH to ATL lands a B−, level with the national rate of 77.6%. Roughly one flight in four arrives 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 375 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,257 at 81.9% on time.

United Airlines is the most reliable of the three carriers covered here at 81.9% on time across 1,257 flights.

On time

77.4%

Arrivals under 15 minutes late, of 359 completed flights

Avg delay

58 min

Across delayed arrivals only, not all flights

Cancelled

4.27%

National rate is 1.81%

Whole route

77.5%

Every carrier on IAH to ATL, 4,906 flights

These figures cover 375 flights between July 2025 and June 2026. The median arrival is 5 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 ATL

Spirit flew 375 of the 4,906 flights on IAH to ATL, about 8% of it. Its 77.4% on time is about level with the route as a whole at 77.5%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from United at 81.9% to Frontier at 61.7%.

The choice of carrier is not cosmetic here. United Airlines arrives on time 81.9% of the time; Frontier Airlines manages 61.7%. Sample sizes sit next to every figure, because a two-point gap across 767 flights means less than a ten-point one.

On-time performance by carrier on IAH to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	1,257	81.9%	69 min	0.72%	B+
Delta Air Lines	2,507	80.2%	66 min	2.07%	B
Spirit Airlines (this page)	375	77.4%	58 min	4.27%	B−
Frontier Airlines	767	61.7%	68 min	2.22%	D

The spread between United and Frontier is 20 points, wide enough that it should decide the booking. On a hundred trips that is 20 more arrivals inside the on-time window.

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

5am–8am190 flights80.8%
8am–11am14 flights—
11am–2pm51 flights70.0%
2pm–5pm81 flights75.3%
5pm–8pm8 flights—
8pm–5am31 flights73.3%

Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.

The weak window here is the middle of the day, not the evening: 11am–2pm runs 70.0% on time against 80.8% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 5am–8am window is the busiest, with 190 flights scheduled in it.

Across the year

Spirit on IAH to ATL through the year

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

February is the weak month at 67.5% on time, against 96.7% 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. January was the busiest month here, with 48 flights.

Across the week, Wednesday is the strongest day at 93.0% on time and Saturday the weakest at 70.2%. 23 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 44% of the 4,708 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
44%
National Airspace System
33%
Late-arriving aircraft
22%
Extreme weather
1%
Security
1%

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 1,534 minutes out of 4,708, against a national NAS share of 21%. The split is drawn from 4,708 reported delay minutes.

The largest share of delay minutes, 44%, 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 2,050 of the 4,708 delay minutes reported here.

Cancellations run at 4.27%, against 1.81% nationally. That is about one flight in 25 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here costs

7.2% 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 last about an hour, which a normal layover absorbs.

The 689 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 is a different operation and performs like one: it runs 66.3% on time across 384 flights, 11 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 11 points of difference.

One caution: this is a thin sample. 375 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 ATL

Put together: the delay figures matter less here than the 4.27% cancellation rate. A late arrival costs you about an hour; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 359 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