Edexcel summer 2013 p-1 physics q no 9 c iii

As it (the paper plane) flies the paper aeroplane loses gravitational potential energy. What happens to this energy?

My answer was : turned into kinetic energy.
But I found in the markscheme that the correct answer is 'lost as heat'. I also found there 'ignore kinetic energy.'
So what is wrong with my answer. Why is kinetic energy said to be ignored??

Please please help me.

When you drop an object like a stone it picks up speed as it falls, as its PE is converted to KE. But what happens when you drop a feather? If you dropped a feather in a vaccuum it would pick up speed just like a rock does, and its PE would be convereted to KE as it falls. But with air resistance what happens? The feather floats gently to the ground, gathering only a small amount of velocity (and small amount of KE) when you initially let go, but then its velocity remains constant for the remainder of the fall. So where does the PE go, if not into KE? Hint: does air resistance come into play here? If so - what happens to energy lost to mechanical resistannce?

I get it. This is y the energy is dissipated as heat and not converted to ke. Thanks a loooooot of the help!