They are squeaking because they are moving as SD said. What happens is a little bit of grit from the sole works itself into the cracks and that starts the squeak with any little bit of movement. A cure is to stop them from moving but that can be almost impossible. Another cure is to clean the edges well and even sand them a bit and oil them with baby oil or some other good oil. Baby oil is suggested because it's cheap and clean as well as smells good.
If your cabin floorboards are removable, they should have some lockdown mechanism anyways... so locking them down so they don't move would stop the squeaking problem more likely than not. If they're actually hatches, check the dogs and see if they can be adjusted.