<Tr> <Th> Type </Th> <Th> Country </Th> <Th> Class </Th> <Th> Role </Th> <Th> Date </Th> <Th> Status </Th> <Th> Notes </Th> </Tr> <Tr> <Td> AVIC 601 - S </Td> <Td> China </Td> <Td> UAV </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Tailless . Series of variants . </Td> </Tr> <Tr> <Td> Boeing X-45C </Td> <Td> US </Td> <Td> UAV </Td> <Td> </Td> <Td> 2002 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Boeing X-48 </Td> <Td> US </Td> <Td> </Td> <Td> </Td> <Td> 2007 </Td> <Td> </Td> <Td> </Td> </Tr>

What is the challenge of creating a blended wing body aircraft