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We propose a hybrid channel estimation process for orthogonal frequency division multiplexing (OFDM) systems. We show that the OFDM channel estimation process can be substantially improved by using a blind estimation module, namely the expectation-maximization (EM) algorithm, in addition to a conventional non-blind estimation module such as pilot symbol-aided channel estimation (PSAC). We provide a mathematical framework for the EM module and present computer simulations on its performance for an OFDM system operating in a frequency dispersive mobile channel. An additional benefit is revealed by our simulations which show that the proposed method is particularly powerful when the pilot insertion rate, i.e. overhead, is low.