An unidentified jet fighter is seen in the original concepts of Resident Evil 5. As shown by the image, Chris Redfield and Sheva Alomar employ a jet fighter in their final showdown with Albert Wesker inside the volcano. As evidenced by the image, Wesker would have not transformed like in the final build, instead retaining his human appearance. It is unknown whether the fighter was player-controllable or not, although it's most likely that it was intended to be fully controllable.
Due to it's design, the fighter in question appears to be a F/A-18D Hornet or a MiG-29A Fulcrum, however due to other existing design (and to keep the cooperative nature of RE5), it appears that the fighter was a Lockheed F-35 Lightning II.