Final answer:
A propeller-driven airplane for a day VFR flight should have enough fuel to reach the destination, then fly for an additional 30 minutes during the day or 45 minutes during the night, taking into consideration weather conditions and possible delays. Various factors influence fuel consumption, and it's not simply proportional to the distance covered.
Step-by-step explanation:
The correct answer is that there should be enough fuel on board a propeller-driven airplane for a day VFR flight to take into account meteorological conditions and any foreseeable delays. In fact, the Federal Aviation Regulation (FAR) provides a rule: during the day, you must have enough fuel to reach your destination and then fly for 30 minutes at cruising speed. At night VFR, you must have enough to fly to your destination and then for an additional 45 minutes.
For example, let's consider a trip from San Diego to San Francisco which is about 700 km. Using a plane efficiency of about 70 miles per gallon (m.p.g) per passenger for 80% full airplane as mentioned in the referenced information, the fuel needed would vary based on the number of passengers and plane's fuel efficiency. Taking into consideration the plane's load and weather conditions, these factors could significantly modify fuel consumption.
It's important to mention that fuel requirements do not simply scale with distance, especially in air travel. Factors like altitude, air resistance, payload and switching on and off the engines have a significant impact on fuel consumption.
Learn more about Aircraft Fuel Requirements