The present invention relates to a method of increasing replication of a reassortant influenza virus by at least 10%, the method comprising the steps of: i) comparing the amino acid sequence of the reassortant influenza virus with the amino acid sequence of a different influenza virus, which different influenza virus grows in embryonated eggs and ii) substituting as needed HA H3 amino acid residues such that position 186 is a valine and position 226 is an isoleucine. The present invention further relates to a replication enhanced reassortant influenza virus comprising an HA H3 protein comprising a valine at position 186 and an isoleucine at position 226. Furthermore, the invention relates to an immunogenic composition comprising the replication enhanced reassortant influenza virus comprising an HA H3 protein comprising a valine at position 186 and an isoleucine at position 226.