One movement holds the whole word: something passes above something else and never touches it. Planes come in low over the heads of a crowd and are gone. A road is lifted and carried across the top of another road, and neither line of traffic has to stop. Even 'flyover country' is that same view from the plane window — land you only ever cross above. The word was made straight out of the verb 'fly over', and passing above is what it kept.
The source gives the noun as deverbal from 'fly over', so the noun is simply the action turned into a thing.
來源說這個名詞是直接從動詞片語 fly over 變來的。所以它不是先有東西才有動作，而是先有「從上方飛過」這個動作，然後整個動作被裝成一個名詞。
Wiktionary via kaikki (source_ref kaikki:3f6f69a190036ae4:1442192652:13821): "Deverbal from fly over."
Two branches
從天上飛過去
這一支保留了字面的飛：真的有東西在天上經過。
noun · B2
A flight by a group of planes, usually military ones, that passes low over a place so that the people below can watch it, normally as part of a ceremony or celebration. This is the American English use; British English says flypast.
編隊飛越
路從上面跨過去
同樣是「從上方越過」，只是越過的東西換成一條路，而且它停在那裡不動。
noun · B1
A bridge that carries one road, or a railway line, over another road, so that traffic on both can keep moving. This is the British English use, and it is used in the same way in Ireland, in Commonwealth countries and in the Philippines.
陸橋