Where would a fly go with no sensory input?

So 4 or five of them are buzzing around my light, turning at what I presume is an input of some sort - optical, olfactory etc…

If I put one of them in a huge dark tank with no wind currents, the right mix of pure oxygen / CO2 for it to breathe, no noises or smells, even temperature all over etc would it fly in a straight line??

For the purpose of this question the tank is infinite (so it won’t hit a wall)…

What would happen?

Bump!

They’re still there.