They do have extra blankets & egg crates available. My 10 year old ( at the time ) found it so bad that she cried.... Even after adding the extra blankets & egg crates it was unusable ( not too mention filthy and unmade when we boarded, but that is another story ).
We moved her into the murphy bed and all was fine.
Unless they have changed them out, I don't think many adults will find it acceptable.