We show that the following classes of lattice polytopes have unimodular covers, in dimension three: the class of parallelepipeds, the class of centrally symmetric polytopes, and the class of Cayley sums Cay(P, Q) where the normal fan of Q refines that of P . This improves results of Beck et al. (2018) and Haase et al. (2008) where the last two classes were shown to be IDP.