Benedict’s helicopter ride was very unlike Nixon’s. Nixon boarded Marine One, took off, and never came back to the White House. Nixon resigned, properly and validly. He resigned the Office. He signed a document that was short and to the point. Benedict COULD have resigned validly, had he followed Nixon’s example.
Instead, he tried to resign only the ministry – the governance – the “doing,” while trying to remain somehow as the hidden contemplative papal member, keeping the title “His Holiness.” Not strange at all.
Benedict’s helicopter didn’t really take him anywhere. Nine years later, still inside the Vatican.