Step-by-step explanation:
As the plane accelerates in its climb towards its cruising altitude, the weight of the plane and its passengers is less as compared to on the earth's surface. The mass, nonetheless, remains the same.
The reason for the change in weight is because as the plane accelerates upwards, it cancels out most of the acceleration by gravity (10m/s²). Gravity applies downwards towards the earth's surface.
Remember that weight is equal to mass * gravity
Reduced gravitational acceleration, will therefore mean a reduction in weight even as mass remains the same.