Every pilot learns early on in flight training that it’s essential to have the appropriate quantity of fuel on board. Anyone who has run out of gas in their car understands this lesson well, but the consequences of fuel issues in an aircraft are much more dire. And there are several factors to consider when determining the minimum amount of fuel acceptable for any given flight.

When calculating fuel burn, round up. The numbers in the flight manual are for new aircraft, so it’s necessary to add extra to account for the age and performance of your aircraft if it is not brand new.

Weather also affects fuel burn, so consider headwinds (or tailwinds!) in your flight planning. When flying into headwinds it will take you longer to reach your destination; therefore, you will need more fuel. FAR 91.151 requires VFR pilots to fly with enough fuel to fly to their destination and then 30 minutes after that (45 minutes for night VFR flights).

During the flight planning process, add extra fuel for the factors that you can’t know ahead of time. For example, you will burn more fuel if unforecast weather requires you to deviate around it. And you never know if an incident may close your destination airport while you are en route, which would require you to turn back to your departure airport or deviate to another airport—all of which burns more fuel than expected.

So why not just fill the tanks before each flight? That may be the best decision for some flights, but it depends on the aircraft’s weight and balance. If you are the only occupant and there is no additional cargo on board, the airplane likely will carry full fuel with no problem. Add in a couple of passengers plus baggage, and the equation completely changes. Topping off the tanks may no longer be an option. You must exercise judgment and carry at least enough fuel to meet the legal requirement, as well as any additional fuel necessary to ensure safety of flight. It's a delicate balance (pardon the pun) but the bottom line when dealing with fuel is to always carry as much as possible.

Lastly, always visually check the quantity and quality of the fuel during the preflight inspection. Too many accidents have happened as a result of pilots trusting fuel gauges that were inaccurate or “believing” there was enough fuel in the tanks.