2D physics problem

I am making a paper plane game and when i click or touch and hold the screen i want my plane to continue going up at constant velocity, and when i let go the plane glides down. At the moment my plane is doing what flappy bird did, if i click/touch and hold it only hops up once and then stars falling. Is this the way i am using my input or is it the physics?

I beleive that u need to do get button down (button…) ect. Sometimes the other things dont mean hold like get key down(input…) would mean click not hold. It happened to me in my fps game so i used it to meh advantage by making both a pistol and machine gun. Any ways, see if it works and if not then post the script so i can look at it further