Preflight Preparation
What the regulation actually requires
14 CFR 91.103 launches nearly every preflight question: before departure the pilot in command must become familiar with all available information concerning the flight. In practice that means weather, fuel, alternatives, runway lengths, takeoff/landing performance, and weight and balance. Questions love to test whether you know the difference between the documents that must be aboard the aircraft (airworthiness certificate, registration, operating limitations, weight and balance data, and - for most operations - the FCC radio license) and those the pilot must hold (certificate, medical, photo ID).
Inspection and equipment traps
Know the calendar-month intervals cold: annual inspection every 12 calendar months, 100-hour for aircraft carrying persons for hire, pitot-static/altimeter/encoder and transponder checks every 24 calendar months for IFR, VOR check every 30 days. A common distractor converts 'calendar months' into 'days.'
Fuel and alternate planning
VFR day: enough to reach the first point of intended landing plus 30 minutes; VFR night adds 45 minutes. IFR: destination, approach, missed approach, alternate, plus 45 minutes at normal cruise. An alternate is not required when the destination forecast, at ETA ±1 hour, shows ceiling at least 2,000 ft above airport elevation and visibility at least 3 SM.
Worked example - the 1-2-3 rule: ETA 1500. Forecast 1400–1600 shows ceiling 800 ft overcast, visibility 4 SM. Visibility is fine, but ceiling is below 1,000 ft inside the window, so an IFR alternate is required. Weather at the alternate must then meet its own minimums.
Rule of thumb: ceiling and visibility are judged in the ±1-hour window, never at a single forecast hour.