Marines “aggressor” squadrons in training exercises, where they simulate the small, low-cross-section (and hence hard to spot) enemies that gave American pilots such trouble in Vietnam . Keeping them in service requires maintenance contracts – and some timely help from the Swiss . F-5 Aggressor Fleet 2010-01-12T15:37:00-08:00 V2 1950s|Air Force|Aircraft|Navy|Top Gun|United