The official reason for the trip to the mid-East is that eternal chimera of popes: union with the Orthodox:
But the official purpose of the visit is to commemorate the 50th anniversary of a historic rapprochement between Catholics and Orthodox and to try to restore Christian unity after nearly 1,000 years of estrangement.
Meeting in Jerusalem in 1964, Pope Paul VI and Orthodox Patriarch Athenagoras set a milestone: They started the process of healing the schism between Eastern and Western Christianity of the year 1054.
Go here to NPR to read the rest. Popes have taken these types of initiatives many, many times over the past thousand years and they always come a cropper on one rock hard fact: the Orthodox, at least those who call the shots in the various Orthodox churches, are simply not interested in union with Rome.