There actually IS a difference between "manneuvering speed" (Va) and "rough
air penetration speed" also known as "maximum structural cruising speed" (Vno).
  

Maneuvering speed is the highest speed where you can't bend the airplane by
pulling back on the stick.  The wing stalls at maximum design load factor.

The rough air penetration speed is the highest speed where an FAA-specified
gust factor will not bend the airplane.  It's not the same thing.

Since the gust may not be as effective at raising the angle-of-attack of the
wing as hauling back on the stick, Vno is sometimes higher than Va.  In my
Cessna 150, for example, Va is 109 mph and Vno is 120 mph.  (Not that I care
about that since I couldn't cruise that fast anyway...)  An important thing to
remember is that Mother Nature doesn't care what the FAA says, and there may be
gusts out there higher than the FAA designated "highest likely gust".  Like,
for instance, in a thunderstorm.

You are always protected against breaking your wing by flying at Va -- not so
at Vno.

- Rob Wolf