code: def altitude(msg):
      
  
      tc = common.typecode(msg)
  
      if tc<9 or tc==19 or tc>22:
          raise RuntimeError("%s: Not a airborn position message" % msg)
  
      mb = common.hex2bin(msg)[32:]
  
      if tc < 19:
          # barometric altitude
          q = mb[15]
          if q:
              n = common.bin2int(mb[8:15]+mb[16:20])
              alt = n * 25 - 1000
          else:
              alt = None
      else:
          # GNSS altitude, meters -> feet
          alt = common.bin2int(mb[8:20]) * 3.28084
  
      return alt
docs: Decode aircraft altitude
  
      Args:
          msg (string): 28 bytes hexadecimal message string
  
      Returns:
          int: altitude in feet