Route profile
IAH→SEA
Flight reliability, delays and best times to fly from Houston to Seattle, 1,874 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 50% of comparable major US routes (4,598 compared)
Calculated from 6,529 flights. How this is calculated
IAH → SEA arrives on time 77.4% of the time; the return trip, SEA → IAH, arrives on time 79.4% of the time, a 2.0-point gap between the two directions of the same city pair.
IAH → SEA spends 33.1 minutes on the ground on a 1,874-mile trip: 20.6 minutes from pushback to wheels-up at IAH and 12.4 minutes from touchdown to gate at SEA.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What sets this route apart
Where IAH to SEA differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
IAH to SEA struggles most at 5 PM: 60.5% of its flights scheduled then arrive on time, 12.5 points behind the 73.0% on routes of similar length at the same hour. Against all other routes the gap is 9.3 points.
IAH to SEA is at its best against routes of similar length for flights scheduled at 4 PM: 78.4% arrive on time, 6.2 points ahead of the 72.2% those routes manage at that hour. Against all other routes the gap is 7.7 points.
In June, IAH to SEA runs 4.8 points below routes of similar length, 67.8% on time to 72.6%. Against all other routes the gap is 4.9 points.
United Airlines’ flights on IAH to SEA arrive on time 76.4% of the time, 3.7 points below the 80.1% it manages on its routes of similar length. Against all other routes the gap is 3.5 points.
Alaska Airlines does better on IAH to SEA than on its routes of similar length: 78.7% on time here, 76.1% there, 2.6 points apart.
IAH to SEA against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 5 PM departures | 60.5% | routes of similar length | 73.0% | −12.5 pts | 220 here, 77,464 there |
| Hour: 4 PM departures | 78.4% | routes of similar length | 72.2% | +6.2 pts | 893 here, 61,562 there |
| Month: June | 67.8% | routes of similar length | 72.6% | −4.8 pts | 649 here, 104,738 there |
| Airline: United Airlines | 76.4% | routes of similar length | 80.1% | −3.7 pts | 3,762 here, 252,486 there |
| Airline: Alaska Airlines | 78.7% | routes of similar length | 76.1% | +2.6 pts | 2,673 here, 92,871 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 1,874 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
Why IAH → SEA flights are cancelled
July 2023 – July 2026
IAH → SEA cancelled 76 of 6,529 scheduled flights — about 1 in every 86. The reason filed most often was the airline, 59.2% of the cancellations coded on this route — about 1 in every 145 scheduled flights.
Share of cancellations
Of 76 cancelled departures carrying a reason code.
What each reason means
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
45 cancellations, 59.2% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
27 cancellations, 35.5% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
4 cancellations, 5.3% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. With only one or two carriers on the route, the split mostly reflects how they file. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
76 coded cancellations were recorded on IAH → SEA; the section appears from 50.
When it goes wrong
July 2023 – July 2026
43 min late
against a median of 4 min early
Percentiles over 6,529 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SEA after arriving from IAH.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 41% | Likely to miss |
| 45 min | 22% | High risk |
| 60 min | 14% | Some risk |
| 90 min | 7.0% | Some risk |
| 120 min | 3.8% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.16% of the time and diverts 0.25% of the time, which a late arrival never shows up in.
Chance of missing is the share of 6,437 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 43 minutes late (90th-percentile gate arrival delay), over 6,529 operations.
Any other layover length: connection checker.
Best time to fly
IAH → SEA flights departing 5–9 AM arrived on time 87.0% of the time, against 67.8% for 6–9 PM departures, a gap of 19.2 percentage points.
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 90.0% on time from 547 flights
- 7 AM: 84.9% on time from 832 flights
- 8 AM: 87.2% on time from 288 flights
- 9 AM: 85.0% on time from 892 flights
- 10 AM: 77.6% on time from 485 flights
- 11 AM to 3 PM: too few flights to score
- 4 PM: 78.4% on time from 901 flights
- 5 PM: 60.5% on time from 224 flights
- 6 PM: 69.9% on time from 827 flights
- 7 PM: 68.1% on time from 931 flights
- 8 PM: 62.8% on time from 403 flights
- 9 PM to 11 PM: too few flights to score
Departure windows with fewer than 120 flights are not scored.
Why IAH → SEA runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for IAH → SEA. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on IAH → SEA, at 40.6%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 87.0% of the time and 6–9 PM departures 67.8%.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| United Airlines | 3,808 | 76.4% | 0.95% | -3 min | 8.5% |
| Alaska Airlines | 2,719 | 78.7% | 1.47% | -5 min | 5.2% |
United Airlines flew 58.3% of the 6,527 flights listed.
Alaska Airlines arrived on time 2.3 percentage points more often than United Airlines on this route.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Sunday the least, a gap of 6.0 percentage points.
By month
- Jan: 74.7%
- Feb: 81.7%
- Mar: 78.8%
- Apr: 81.0%
- May: 72.9%
- Jun: 67.8%
- Jul: 71.4%
- Aug: 76.8%
- Sep: 84.5%
- Oct: 84.3%
- Nov: 82.4%
- Dec: 81.1%
June is historically the weakest month and September the strongest, a spread of 16.7 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 75.6% from 212 flights
- August 2023: 85.4% from 213 flights
- September 2023: 79.8% from 178 flights
- October 2023: 84.5% from 182 flights
- November 2023: 83.1% from 160 flights
- December 2023: 90.3% from 155 flights
- January 2024: 70.8% from 140 flights
- February 2024: too few flights to score (116)
- March 2024: 81.8% from 149 flights
- April 2024: 74.5% from 162 flights
- May 2024: 60.1% from 214 flights
- June 2024: 66.5% from 214 flights
- July 2024: 62.6% from 248 flights
- August 2024: 76.5% from 233 flights
- September 2024: 87.1% from 204 flights
- October 2024: 88.1% from 168 flights
- November 2024: 86.6% from 142 flights
- December 2024: 83.0% from 155 flights
- January 2025: 78.0% from 130 flights
- February 2025: too few flights to score (112)
- March 2025: 78.5% from 150 flights
- April 2025: 78.4% from 150 flights
- May 2025: 72.4% from 187 flights
- June 2025: 62.7% from 229 flights
- July 2025: 67.1% from 236 flights
- August 2025: 68.9% from 228 flights
- September 2025: 85.9% from 199 flights
- October 2025: 80.5% from 175 flights
- November 2025: 77.7% from 148 flights
- December 2025: 70.7% from 169 flights
- January 2026: 75.2% from 134 flights
- February 2026: too few flights to score (112)
- March 2026: 76.1% from 144 flights
- April 2026: 90.7% from 150 flights
- May 2026: 88.0% from 183 flights
- June 2026: 74.2% from 217 flights
- July 2026: 80.9% from 231 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 79.0% against 76.8% in the 12 months before — improving by 2.2 percentage points.
Data and methodology
Calculated by FlyerIntel from 6,529 IAH → SEA flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed