A tanker aircraft capacity extension system shaped to fit within an aircraft cargo area may include a first portable fuel container having a first outlet port adapted to connect to an integral fuel system of the aircraft, and a first inlet port; and a second portable fuel container having a second outlet port adapted to connect to the first inlet port and a second inlet port adapted to connect to a third fuel container; when the second outlet port is connected to the first inlet port and the first outlet port is connected to the integral fuel system of the aircraft, fuel flows from the second fuel container, through the outlet port to the first inlet port into the interior of the first container, and out from the first outlet port of the first container.

A tanker aircraft capacity extension system shaped to fit within an aircraft cargo area may include a first portable fuel container having a first outlet port adapted to connect to an integral fuel system of the aircraft, and a first inlet port; and a second portable fuel container having a second outlet port adapted to connect to the first inlet port and a second inlet port adapted to connect to a third fuel container; when the second outlet port is connected to the first inlet port and the first outlet port is connected to the integral fuel system of the aircraft, fuel flows from the second fuel container, through the outlet port to the first inlet port into the interior of the first container, and out from the first outlet port of the first container.

An aircraft propulsion unit comprising a motor, a system for supplying fuel to the motor, a fairing inside which the motor and at least part of the fuel supplying system are positioned, and at least one pressure relief device configured to establish communication between the inner and outer zones of the fairing when the pressure in the inner zone is greater than or equal to a given threshold or when a leak is detected. Also an aircraft comprising at least one such propulsion unit.