Here's the vocal part in "Passing By" (the top two lines are the "verses"; the bottom line is the coda):
Here's the vocal part (starting at ~1:02) in the Beatles' "Flying":
There's some degree of similarity in the beginnings of the phrases: an initial fourth or third, the second note of which starts a conjunct group of notes, usually all ascending. More idiosyncratic, though, is the sort of skipping rhythm in both (in the even-numbered measures of "Passing By" but the odd-numbered measures of "Flying"): quarter note, eighth note, quarter note, eighth note, quarter note. Of course, both vocal parts are also wordless.
The titles are similar, too; both are either gerunds or participles that describe movement.