Related Clues:

• Early all-metal bomber
• Vitamin ___ (PABA)
• Old Army bomber plane
• Bygone bomber whose name is a call in bingo
• Innovative all-metal bomber of the 1930s
• Bingo call or bomber
• Leftmost-column number
• Airplane whose name is also a vitamin
• Apt bingo call to lose on, by the sound of it?