Spirits do not have flesh, obviously... That's precisely why Jesus had to materialize bodies of flesh to make himself visible to his disciples and show them that it was he himself who had come back to life.
The simple fact that he sometimes appeared physically different, unrecognizable, shows that he did not always use a body similar to his before he died... if that had been the case he would have always been recognizable, and would not have even needed to show marks on his hands and side, if his face and physical bearing had already been enough. In fact, the marks on his old body of flesh were not limited to his hands, side and feet, as he had been mistreated long before he died, on his back from whipping, on his forehead the marks from thorns, etc.
Furthermore, the fact that he disappeared in front of them showed them that he was no longer a man with a fleshly body, but a spirit, like the angels of ancient times who appeared materialized and then disappeared. The Jews know these stories well. Angels do not have flesh because they are spirits, and thus his disciples would understand that the new resurrected Jesus was no longer a human of flesh, but a spirit that appeared and disappeared.
