How old is he? Did he had any training ? -at home or by a proffesional? ,could you tell us what are his triggers? -even when there is no reason -there always is a motive behind it?
How does his body posture look before he jump? Are you sure its aggression or just playful nipping (both are a no no but there is a big difference between both )
So sorry to ask all those questions but i feel we need to have a clearer picture before sone of us attempt to find the solution.
Failing that -dog behaviourist might be really handy in your situation x