Re: How hot would this aircraft get?

At the speed of light?  No even in deep space.  That would require infinite
energy to accelerate the person to that speed.

As far as aircraft, you're talking about insane amounts of energy but also
material impossibility.  There are approximately 25,000,000,000,000,000,000
molecules per cubic centimeter at atmospheric pressure, all of which would
be moving at energies far exceeding the binding energy of atoms in their
molecular matrix by many millions or billions of times as you went close to
the speed of light, which would tear through the "aircraft" in question in
nanoseconds (literally, at close to the speed of light 1ft is approximately
1 ns).

On top of that ridiculousness, at close to the speed of light you'd be in
and out of the atmosphere of the Earth (having been thoroughly evaporated
into a stream of particles by the impact) in milliseconds with no force in
the universe able to keep you in the atmosphere.  Close to speed of light
travel is only remotely possible at the distances of interstellar travel as
well as the vacuum of deep space, and even then enormously technologically
challenging for us as a species.

In short, no, no, and more no on going even close (anything much higher
than the aircraft speed record of approximately 0.0007% of the speed of
light) of the speed of light.  The difficulties get insanely higher after
the current speed records, which were essentially already set by a rocket
"aircraft" that was really already mostly in the vacuum of space.