Ever since the Europeans signed on to the F-35 program, it has been clouded by one persistent fear: that in some future geopolitical crisis, Washington might seek to exercise leverage by denying software updates or spare parts, thereby rendering the European fleet inoperable. But where does this geopolitical anxiety come from? Is it grounded in historical fact (i.e., have there been precedents in which the United States weaponized its control over advanced weapon systems against its allies)?