Answer : speed
Explanation :
Speed is defined as the distance travelled per unit time. It is a scalar quantity.
Velocity is displacement covered per unit time. It is a vector quantity. This means it have both magnitude as well as direction.
When captain told the passengers that the plane is flying at 450 miles per hour, then this shows the speed of plane. He is not talking about the direction in which the plane is flying.
So, this information describes the speed of plane.
Correct option is (2).