Non uniform acceleration?

As the object is falling at greater velocity the drag created by air is greater. So the acceleration at the beginning is equal to the acceleration due to gravity or 9.81 ms^-1. As the velocity increases the drag also increases so acceleration decreases (by the equation a = F(total)/m). Drag is also a force. So acceleration/time graph would be something like a/t)=sqrt(t*k)=(t*k)^1/2 where k is a constant