- Aircraft system with assisted take-off and climbing, comprising: a main air vehicle capable of performing autonomously the cruising and landing phases of a flight, an auxiliary air vehicle lighter than the main air vehicle and adapted to assist the main air vehicle during the taxing and take-off phases of a flight, wherein the main and auxiliary air vehicles (1, 2) are adapted to be detachably connectable, so that the auxiliary air vehicle can assist the main air vehicle when both are attached to each other during taxing, take-off and climbing, characterized in that: - the auxiliary air vehicle is an unmanned air vehicle and it is further adapted to fly and land when it is detached from the main air vehicle, - the main air vehicle has a nose landing gear and main landing gear including left and right landing gears and wherein the main and auxiliary air vehicles (1, 2) are adapted so that the auxiliary air vehicle is detachably connectable to the belly of the main air vehicle and between the left and right landing gears, and - the auxiliary air vehicle has a landing gear, wherein the main and auxiliary air vehicles (1, 2) are configured such as when they are both connected during taxing and take-off, the landing gear (6, 5) of both air vehicles (1, 2) are extended and on the ground, and the auxiliary air vehicle partially supports the weight of the main air vehicle. a main air vehicle capable of performing autonomously the cruising and landing phases of a flight, an auxiliary air vehicle lighter than the main air vehicle and adapted to assist the main air vehicle during the taxing and take-off phases of a flight, wherein the main and auxiliary air vehicles (1, 2) are adapted to be detachably connectable, so that the auxiliary air vehicle can assist the main air vehicle when both are attached to each other during taxing, take-off and climbing, characterized in that: - the auxiliary air vehicle is an unmanned air vehicle and it is further adapted to fly and land when it is detached from the main air vehicle, - the main air vehicle has a nose landing gear and main landing gear including left and right landing gears and wherein the main and auxiliary air vehicles (1, 2) are adapted so that the auxiliary air vehicle is detachably connectable to the belly of the main air vehicle and between the left and right landing gears, and - the auxiliary air vehicle has a landing gear, wherein the main and auxiliary air vehicles (1, 2) are configured such as when they are both connected during taxing and take-off, the landing gear (6, 5) of both air vehicles (1, 2) are extended and on the ground, and the auxiliary air vehicle partially supports the weight of the main air vehicle. - the auxiliary air vehicle is an unmanned air vehicle and it is further adapted to fly and land when it is detached from the main air vehicle, - the main air vehicle has a nose landing gear and main landing gear including left and right landing gears and wherein the main and auxiliary air vehicles (1, 2) are adapted so that the auxiliary air vehicle is detachably connectable to the belly of the main air vehicle and between the left and right landing gears, and - the auxiliary air vehicle has a landing gear, wherein the main and auxiliary air vehicles (1, 2) are configured such as when they are both connected during taxing and take-off, the landing gear (6, 5) of both air vehicles (1, 2) are extended and on the ground, and the auxiliary air vehicle partially supports the weight of the main air vehicle.