80% of flights from Houston to Seattle arrived on time over the past 12 months. That is about the typical U.S. route. The 6 a.m. departures ran on time 92% of the time; the 6 p.m. ones 70%. Most reliable airline: Alaska Airlines (81%). 5% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for IAH → SEA: when a flight was late, it was under 45 minutes late 63% of the time. About 1 in 21 flights landed an hour or more late, and 1 in 188 three hours or more; 0.2% were cancelled outright.
- On time or early80%
- 15–30 min late8.2%
- 30–60 min late6.2%
- 1–2 hours late3.3%
- 2–3 hours late1.0%
- 3+ hours late0.5%
- Diverted0.1%
- Cancelled0.2%
Share of all 2,072 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| United Airlines | 1,230 | 80% | 0.1% | −5 min | 5.7% | +52 min | United Airlines |
| Alaska Airlines | 842 | 81% | 0.5% | −5 min | 3.7% | +52 min | Alaska Airlines |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at IAH). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | United Airlines | Alaska Airlines |
|---|---|---|
| 6 a.m. | — | 92% |
| 7 a.m. | — | 82% |
| 8 a.m. | — | 84% |
| 9 a.m. | 84% | — |
| 10 a.m. | 79% | — |
| 2 p.m. | — | 85% |
| 4 p.m. | 78% | — |
| 6 p.m. | 75% | — |
| 7 p.m. | 76% | 70% |
| 8 p.m. | 76% | — |
Last flight of the day
On IAH → SEA, each airline's last flight of the day was cancelled 0.3% of the time, against 0.2% for its earlier flights, about the same. It arrived 3+ hours late 0.7% of the time (earlier flights: 0.5%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| Alaska Airlines | 2:38 p.m. | 0.3% | 1.1% | 0.6% | first flight 6:02 a.m. |
| United Airlines | 6:45 p.m. | 0.3% | 0.3% | 0.0% | first flight 8:00 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
By month
Each calendar month pooled over 2023–2026. Best: September (84%). Worst: June (67%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 309 | 80% | 0.3% |
| Tuesday | 281 | 84% | 0.0% |
| Wednesday | 281 | 81% | 0.0% |
| Thursday | 307 | 85% | 0.0% |
| Friday | 307 | 78% | 0.7% |
| Saturday | 284 | 76% | 0.0% |
| Sunday | 303 | 78% | 0.7% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 3 · airline 2
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| AS 453 | 7:00 a.m. | 334 | 86% | 0.9% | −9 min | Alaska Airlines |
| UA 2205 | 9:50 a.m. | 156 | 79% | 0.0% | −7 min | United Airlines |
| AS 439 | 2:38 p.m. | 361 | 76% | 0.3% | −3 min | Alaska Airlines |
| UA 2638 | 4:25 p.m. | 123 | 70% | 0.0% | −1 min | United Airlines |
| UA 2456 | 7:57 p.m. | 280 | 74% | 0.4% | −1 min | United Airlines |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Nov 24, 2025 | 5 | 0% | 0 |
| Mar 13, 2026 | 5 | 20% | 1 |
| Nov 30, 2025 | 5 | 20% | 0 |
| Mar 16, 2026 | 5 | 20% | 0 |
| Dec 8, 2025 | 5 | 20% | 0 |
Questions
How often are flights from IAH to SEA on time?
80% of 2,072 scheduled flights from Houston, TX to Seattle, WA arrived within 15 minutes of schedule between September 2025 and August 2026. 0.2% were cancelled.
What is the best time of day to fly IAH to SEA?
Flights scheduled to leave at 6 a.m. were the most reliable (92% on time). The 6 p.m. departures were the least (70%).
Which airline is most on time from IAH to SEA?
Alaska Airlines: 81% of its 842 flights on the route arrived on time. United Airlines: 80%.
What month has the most delays from IAH to SEA?
June (67% on time). The best month is September (84%), over 2023–2026.
Is the last flight of the day from IAH to SEA more likely to be cancelled?
Not much. Each airline's last IAH–SEA flight of the day was cancelled 0.3% of the time over the past year, against 0.2% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- SEA → IAH (return)
- Houston Bush Intercontinental (IAH) delays by hour
- Flights into Seattle-Tacoma (SEA)
- United Airlines on-time record
- Alaska Airlines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.