The weight (mass) of matter does not change while in an airplane flying in the air. According to the principle of physics known as the conservation of mass, matter cannot be created or destroyed. It can only change form. Therefore, the mass of the matter remains constant regardless of its location, whether on the ground or in an airplane flying through the air.

However, it is important to distinguish between mass and weight. Mass is a measure of the amount of matter an object contains, while weight is a measure of the force exerted on an object due to gravity. While the mass of an object remains the same, its weight can vary depending on the gravitational field it is in.

In the case of an airplane, the force of gravity is still acting on the matter within the plane. Therefore, the matter still has weight even though it is not in direct contact with the ground. However, the weight of the matter may be reduced slightly due to the upward lift generated by the wings of the airplane. This lift counteracts some of the force of gravity, resulting in a slightly reduced weight for the matter inside the plane compared to its weight on the ground.