Carrier route record

UAIAH→ATL

United Airlines · Houston to Atlanta

Flights: 1,257
Period: July 2025 to June 2026
Share of route: 26%
Carriers: 4

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

United on IAH to ATL lands a B+, 4 points better than the national rate of 77.6%. About one flight in six arrives 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 1,257 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,507 at 80.2% on time.

Set against the rest of the country, United's IAH to ATL record is 4 points better than the US average of 77.6%. That gap is worth roughly 43 fewer late arrivals for every thousand flights.

On time

81.9%

Arrivals under 15 minutes late, of 1,247 completed flights

Avg delay

69 min

Across delayed arrivals only, not all flights

Cancelled

0.72%

National rate is 1.81%

Whole route

77.5%

Every carrier on IAH to ATL, 4,906 flights

These figures cover 1,257 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

United against every carrier on IAH to ATL

United flew 1,257 of the 4,906 flights on IAH to ATL, about 26% of it. Its 81.9% on time is 4 points better than the route as a whole, which runs 77.5%. Ranked by on-time rate it is first 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. Delta Air Lines arrives on time 80.2% 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 (this page)	1,257	81.9%	69 min	0.72%	B+
Delta Air Lines	2,507	80.2%	66 min	2.07%	B
Spirit Airlines	375	77.4%	58 min	4.27%	B−
Frontier Airlines	767	61.7%	68 min	2.22%	D

Spirit Airlines cancels 4.3% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.

Departure window

When United runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 25 points, against 19 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am305 flights93.7%
8am–11am—
11am–2pm236 flights86.0%
2pm–5pm250 flights80.2%
5pm–8pm252 flights69.2%
8pm–5am214 flights77.3%

Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.7% of the time, against 69.2% for the evening window. That is 25 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 305 flights scheduled in it.

Across the year

United on IAH to ATL through the year

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

June is the worst month at 68.4% on time, 24 points below February, the best at 91.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. April was the busiest month here, with 141 flights.

Across the week, Tuesday is the strongest day at 87.8% on time and Friday the weakest at 74.2%. 14 points is a smaller lever than departure hour, but it is free.

Delay causes

Why United 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 16,000 reported delay minutes.

Late-arriving aircraft
38%
Carrier
34%
National Airspace System
22%
Extreme weather
6%

38% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 16,000 reported delay minutes here, that single category outweighs weather by 7 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 15,642 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 93.7% on time here.

Cancellations are rare at 0.72%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

6.5% 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 a little over 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 85.1% on time across 1,255 flights, 3 points above 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 3 points of difference.

The sample behind these figures is 1,257 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 United on IAH to ATL

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 91.9% on time and June 68.4%, a swing of 24 points. If the dates move at all, move them out of June before you think about anything else. 1,247 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