Carrier route record

ASIAH→SEA

Alaska Airlines · Houston to Seattle

Flights: 852
Period: July 2025 to June 2026
Share of route: 41%
Carriers: 2

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

Alaska on IAH to SEA 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 about 50 minutes on average. That is a workable record, not a spotless one. That rests on 852 flights, with a median arrival 5 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Alaska on IAH to SEA 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 845 completed flights

Avg delay

51 min

Across delayed arrivals only, not all flights

Cancelled

0.70%

National rate is 1.81%

Whole route

77.5%

Every carrier on IAH to SEA, 2,095 flights

These figures cover 852 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

Alaska against every carrier on IAH to SEA

Alaska flew 852 of the 2,095 flights on IAH to SEA, about 41% of it. Its 78.5% on time is about level with the route as a whole at 77.5%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Alaska at 78.5% to United at 76.8%.

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 SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines (this page)	852	78.5%	51 min	0.70%	B+
United Airlines	1,243	76.8%	56 min	0.40%	B+

Flight by flight

Alaska flight numbers on IAH to SEA

Departure window

When Alaska runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 29 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–8am344 flights87.1%
8am–11am145 flights86.7%
11am–2pm—
2pm–5pm70 flights90.0%
5pm–8pm293 flights61.5%
8pm–5am—

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

The 5pm–8pm window is where this operation falls apart: 61.5% on time, against 90.0% for the 2pm–5pm 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 5am–8am window is the busiest, with 344 flights scheduled in it.

Across the year

Alaska on IAH to SEA through the year

Darker means more delays. Figures are on-time percentages.April best, December worst

December is the weak month at 62.9% on time, against 91.7% in April. 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. July was the busiest month here, with 92 flights.

Across the week, Friday is the strongest day at 83.6% on time and Saturday the weakest at 72.8%. 11 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Alaska runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 46% of the 9,266 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.

Late-arriving aircraft
46%
National Airspace System
32%
Carrier
15%
Extreme weather
5%
Security
1%

46% 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 9,266 reported delay minutes here, that single category outweighs weather by 9 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 9,266 reported delay minutes.

32% 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 3,009 minutes out of 9,266, against a national NAS share of 21%.

Cancellations are rare at 0.70%, 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

Badly late arrivals are rare here: only 4.5% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

At 1,874 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.

The return leg is a different operation and performs like one: it runs 74.3% on time across 852 flights, 4 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 4 points of difference.

One caution: this is a thin sample. 852 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 Alaska on IAH to SEA

Put together: treat all of this as provisional. 852 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. 845 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