A person cannot physically detect motion at constant velocit

A person cannot physically detect motion at constant velocity without external clues so a person sitting in an aircraft or other vehicle with all the windows shut is not aware of movement. So, how is it that a person in an elevator is aware of motion?

Solution

In a lift there is a chane in the normal reaction force acting on the person . But in case of car with windows shutdown there is no Relative change in motion obsered by the person plus there is no change in normal force acting on the person.