 FACT: Air Traffic Control assigns the flight an altitude of 42,000  feet. This is not a permitted flight altitude. At that level,  permitted altitudes are only odd thousands, such as 39,000, 41,000,  or 43,000. Also, those levels are not expressed in feet, but as  "flight levels", referenced to a standard barometric pressure, and  without the last two zeros. E. g. 41,000 feet would be expressed as  "Flight level 410".