<Table> <Tr> <Th_colspan="2"> B - 2 Spirit </Th> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> A U.S. Air Force B - 2 Spirit flying over the Pacific Ocean in May 2006 </Td> </Tr> <Tr> <Th> Role </Th> <Td> Strategic stealth bomber </Td> </Tr> <Tr> <Th> National origin </Th> <Td> United States </Td> </Tr> <Tr> <Th> Manufacturer </Th> <Td> Northrop Corporation Northrop Grumman </Td> </Tr> <Tr> <Th> First flight </Th> <Td> 17 July 1989 </Td> </Tr> <Tr> <Th> Introduction </Th> <Td> April 1997 </Td> </Tr> <Tr> <Th> Status </Th> <Td> In service </Td> </Tr> <Tr> <Th> Primary user </Th> <Td> United States Air Force </Td> </Tr> <Tr> <Th> Produced </Th> <Td> 1987--2000 </Td> </Tr> <Tr> <Th> Number built </Th> <Td> 21 </Td> </Tr> <Tr> <Th> Program cost </Th> <Td> US $44.75 billion (through 2004) </Td> </Tr> <Tr> <Th> Unit cost </Th> <Td> $737 million (1997 approx . flyaway cost) </Td> </Tr> </Table> <Tr> <Th_colspan="2"> B - 2 Spirit </Th> </Tr>

How much does it cost to make a stealth bomber