Large Crew

Enchant any number of Vehicles you control.
Enchanted vehicles have "You may tap any number of creatures with combined power 3 or greater when
you crew this vehicle. If you do, that creature gets
+2/+2 until end of turn. If this vehicle dies when
it has that +2/+2, you lose 3 life."
The American bombers had more crew and guns than
their British counterparts because America had the population to support a larger crew.