The stress intensity factors are evaluated for a moving planar crack for lo
adings which vary arbitrarily in time and three dimensions of space. We exp
loit the adjoint elasticity equation obeyed by the corresponding weight fun
ctions, and a new and more universal Wiener-Hopf factorization of the Rayle
igh function, this beings the central difficulty in such calculations. For
the mode a weight function we give further asymptotic results crucial to a
subsequent calculation of crack stability with respect to out-of-plane pert
urbations.