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Google·Product Manager·Onsite - Product Sense / Strategy·Intermediate

Intermediate
May 2026

Summary

PM interview at Google with a classic estimation question about SFO airport traffic. Short and focused, nothing too wild.

Questions Asked (1)

Q1

Estimate the number of passengers flying in and out of SFO on a typical day.

Product Analytics & MetricsAdaptability & Ambiguity
Author's notes

I started with US air travel volume and tried to work down to SFO's share based on it being a major west coast hub.

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AI HintsAI Generated

Suggested Approach

Break the problem into supply (runway capacity) and demand (passenger demand) sides, then estimate using a top-down approach. Start with the number of runways and typical aircraft movements per hour, then multiply by average passengers per flight and adjust for peak/off-peak hours. Alternatively, estimate based on population and travel frequency, but the supply-side is often more straightforward for airports.

Pro tip: State your assumptions clearly and round numbers to make calculations easy. Mention that you'd sanity-check with known data (e.g., SFO's annual passenger count is ~50-60 million) to validate your estimate.

1. Clarify the scope

Confirm what 'typical day' means (e.g., average over a year, excluding COVID anomalies) and whether it includes both arriving and departing passengers, and possibly connecting passengers.

2. Choose an estimation approach

Decide between supply-side (airport capacity) or demand-side (population and travel behavior). Supply-side is often easier for airports: estimate runway capacity and flight frequency.

3. Estimate supply-side capacity

SFO has 4 runways, but typically 2 used for arrivals and 2 for departures simultaneously. Assume each runway can handle about 30-40 aircraft per hour. So total aircraft movements per hour ~ 60-80. Multiply by operating hours (e.g., 17 hours) to get daily flights.

4. Estimate passengers per flight

Average aircraft size: mix of narrow-body (150 seats) and wide-body (300 seats). Assume average load factor ~80%. So average passengers per flight ~ 150-200. Multiply by total flights (arrivals + departures) to get total passengers.

5. Calculate and sanity-check

Compute the final number and compare with known data (e.g., SFO handles ~55 million passengers annually, so daily ~150,000). If your estimate is off, adjust assumptions.

Key Points to Mention

  • SFO has 4 runways, but typically operates with 2 arrival and 2 departure runways simultaneously.
  • Runway capacity: ~30-40 aircraft per hour per runway, so total ~60-80 movements per hour.
  • Operating hours: SFO is not 24/7 due to noise curfews; assume ~17 hours of operation.
  • Average aircraft size: mix of narrow-body and wide-body; average ~200 seats.
  • Load factor: average ~80-85% full.
  • Sanity check: SFO's annual passenger traffic is ~50-60 million, so daily average ~140,000-160,000.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.