Route profile
IAH→SFO
Flight reliability, delays and best times to fly from Houston to San Francisco, 1,635 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 47% of comparable major US routes (4,598 compared)
Calculated from 10,331 flights. How this is calculated
IAH → SFO arrives on time 77.1% of the time; the return trip, SFO → IAH, arrives on time 84.3% of the time, a 7.2-point gap between the two directions of the same city pair.
IAH → SFO spends 29.1 minutes on the ground on a 1,635-mile trip: 21.6 minutes from pushback to wheels-up at IAH and 7.5 minutes from touchdown to gate at SFO.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
This route has stayed remarkably steady year over year, a smaller swing than 93% of 5,368 comparable routes.
78.2% on time over the most recent 12 months (2025-08 to 2026-07), against 78.6% in the 12 months before (2024-08 to 2025-07), virtually unchanged.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 5,368 in the comparison.
Why IAH → SFO flights are cancelled
July 2023 – July 2026
IAH → SFO cancelled 97 of 10,331 scheduled flights — about 1 in every 107. The reason filed most often was the airline, 63.9% of the cancellations coded on this route — about 1 in every 167 scheduled flights.
Share of cancellations
Of 97 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.
62 cancellations, 63.9% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
26 cancellations, 26.8% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
9 cancellations, 9.3% 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.
97 coded cancellations were recorded on IAH → SFO; the section appears from 50.
When it goes wrong
July 2023 – July 2026
49 min late
against a median of 6 min early
Percentiles over 10,331 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SFO after arriving from IAH.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 38% | Likely to miss |
| 45 min | 22% | High risk |
| 60 min | 15% | Some risk |
| 90 min | 7.8% | Some risk |
| 120 min | 5.0% | 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 0.94% of the time and diverts 0.07% of the time, which a late arrival never shows up in.
Chance of missing is the share of 10,227 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 49 minutes late (90th-percentile gate arrival delay), over 10,331 operations.
Any other layover length: connection checker.
Best time to fly
IAH → SFO flights departing 5–9 AM arrived on time 89.8% of the time, against 64.5% for 6–9 PM departures, a gap of 25.3 percentage points.
By departure window
By departure hour
- 12 AM to 4 AM: too few flights to score
- 5 AM: 97.2% on time from 826 flights
- 6 AM: 96.7% on time from 123 flights
- 7 AM: 85.6% on time from 1,122 flights
- 8 AM: 72.2% on time from 126 flights
- 9 AM: 72.8% on time from 527 flights
- 10 AM: 76.0% on time from 600 flights
- 11 AM: too few flights to score
- 12 PM: 80.2% on time from 1,039 flights
- 1 PM: too few flights to score
- 2 PM: 81.5% on time from 811 flights
- 3 PM: 71.7% on time from 515 flights
- 4 PM: 76.3% on time from 952 flights
- 5 PM: 78.1% on time from 221 flights
- 6 PM: 68.6% on time from 1,114 flights
- 7 PM: 57.0% on time from 507 flights
- 8 PM: 63.4% on time from 628 flights
- 9 PM: 77.2% on time from 989 flights
- 10 PM: 64.4% on time from 138 flights
- 11 PM: too few flights to score
Why IAH → SFO runs late
July 2023 – July 2026
crew, maintenance, boarding and fueling, all within the carrier’s control
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
Share of the delay minutes US DOT attributed to each cause for IAH → SFO. Only delays of 15 minutes or more are attributed.
How this route holds up in bad weather
July 2023 – July 2026
The harder-hit end is the one the flight leaves from, where a cancellation keeps it from departing at all. Bad weather cancels 3.4 times the normal rate at IAH against 1.7 times at SFO. Cancelled in bad weather against normal hours: IAH 4.1% against 1.2%, SFO 1.5% against 0.9%. Flights that did leave IAH in bad weather arrived on time 63.8% of the time, against 78.6% in normal hours.
Bad weather and normal hours at the airports
Scheduled departures, July 2023 – July 2026| Departures from | IAH | SFO |
|---|---|---|
| Cancelled in bad weather | 4.1% | 1.5% |
| Cancelled in normal hours | 1.2% | 0.9% |
| Arrived on time, bad weather | 63.8% | 73.0% |
| Arrived on time, normal hours | 78.6% | 79.8% |
| Departures in bad weather | 28,922 | 36,006 |
These are airport figures, not route figures: every scheduled departure from IAH and SFO, to any destination, in hours the weather report called bad.
Weather source and limits. In full: IAH, SFO, What Weather Costs Each Airport, Who Cancels More When the Weather Turns, Airports That Change Places When Weather Turns.
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 | 10,331 | 77.1% | 0.94% | -6 min | 8.0% |
Weekly and seasonal patterns
By day of week
Tuesday is historically the most reliable day and Monday the least, a gap of 9.6 percentage points.
By month
- Jan: 79.7%
- Feb: 79.4%
- Mar: 78.5%
- Apr: 74.3%
- May: 67.5%
- Jun: 64.3%
- Jul: 71.1%
- Aug: 83.8%
- Sep: 85.8%
- Oct: 83.6%
- Nov: 80.9%
- Dec: 78.8%
June is historically the weakest month and September the strongest, a spread of 21.5 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 76.6% from 279 flights
- August 2023: 83.2% from 280 flights
- September 2023: 80.8% from 266 flights
- October 2023: 84.8% from 277 flights
- November 2023: 92.2% from 257 flights
- December 2023: 85.0% from 281 flights
- January 2024: 70.6% from 251 flights
- February 2024: 69.4% from 230 flights
- March 2024: 64.9% from 248 flights
- April 2024: 59.4% from 240 flights
- May 2024: 56.6% from 258 flights
- June 2024: 72.8% from 270 flights
- July 2024: 65.4% from 279 flights
- August 2024: 87.9% from 280 flights
- September 2024: 87.0% from 270 flights
- October 2024: 83.9% from 279 flights
- November 2024: 69.4% from 268 flights
- December 2024: 71.4% from 280 flights
- January 2025: 81.4% from 238 flights
- February 2025: 82.0% from 229 flights
- March 2025: 79.6% from 284 flights
- April 2025: 86.6% from 292 flights
- May 2025: 77.9% from 303 flights
- June 2025: 63.7% from 295 flights
- July 2025: 73.9% from 299 flights
- August 2025: 80.5% from 299 flights
- September 2025: 89.3% from 289 flights
- October 2025: 82.2% from 306 flights
- November 2025: 81.6% from 299 flights
- December 2025: 79.7% from 311 flights
- January 2026: 85.2% from 303 flights
- February 2026: 85.5% from 277 flights
- March 2026: 88.5% from 310 flights
- April 2026: 74.2% from 300 flights
- May 2026: 66.4% from 307 flights
- June 2026: 57.2% from 300 flights
- July 2026: 68.2% from 297 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 78.2% against 78.6% in the 12 months before — broadly unchanged.
Data and methodology
Calculated by FlyerIntel from 10,331 IAH → SFO 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