What kind of "gas" do planes use? Where are the tanks located? And how do we decide exactly how much we need for a flight?
The "Gas"
First of all, the fuel used by turbine engines is a type of kerosene, known by various technical codes (such as Jet-A1 or JP-8) depending on its specific properties. If you’ve never seen it, it looks a lot like the fluid used in a Zippo lighter: almost transparent and slightly oily.It has two main advantages: it is highly resistant to low temperatures without freezing (at altitude, outside temperatures can drop below -60°C (below -70F), and it is stable enough not to catch fire easily at high temperatures. In fact, to burn effectively, kerosene must be atomized—turned into a fine mist, like a spray—which is exactly how it’s used inside the engines.
Where are the tanks?
Basically, any space not occupied by something else is a great place to store fuel!
The largest amount is usually contained inside the wings, within a series of tanks distributed along the entire wingspan. Storing fuel in the wings offers several benefits: it makes it easier to keep the aircraft balanced as the tanks empty, and it helps the structure withstand aerodynamic stress and strain. Another advantage for planes with under-wing engines is that in the event of a catastrophic failure where the fuel pumps stop working (an extremely unlikely scenario!), the fuel can still feed the engines by gravity.
Additional tanks are usually located under the cabin floor and sometimes even in the tail section.
How much do we take?
One thing you might not know is that planes almost never "fill it up" before departure. For a "flying machine," keeping weight as low as possible is fundamental. Carrying more fuel than necessary means carrying "dead weight," which increases consumption and, on long flights, could even limit the number of passengers or bags we can carry.
So, how do we know how much to take without risking running dry?
For every flight, a computerized system accurately calculates the expected fuel burn, taking into account the aircraft’s weight, the route, the altitude, the predicted winds, and even the specific engine wear of that individual aircraft. By law, several "reserves" must be added to this amount:
Alternate Fuel: Enough to fly a missed approach at the destination and reach a nearby "alternate" airport (chosen during planning based on weather and availability).
En-route Reserve: Enough to reach an alternate airport at any point along the route if needed.
Contingency Fuel: Extra fuel in case the weather requires route deviations.
Holding Fuel: Enough to "wait" in the air near the destination in case of delays due to traffic, fog, or bad weather.
Final Reserve: A minimum amount that must remain in the tanks upon landing (this varies by aircraft type).
Before every flight, pilots review all the information and decide if the calculated fuel is sufficient or if they need to add more.
"Tankering"
There are special cases where we do try to carry as much fuel as possible. This happens when the fuel price at the departure airport is significantly lower than at the destination—so much so that it justifies the extra weight and higher consumption for that flight.
DontWorryFlyHappy!