Acc. to Gen 9.12-17, God set a rainbow in the clouds as the sign that
he would never again destroy the Earth with a flood. Isaac Asimov speculated
that the Flood may have been caused by a large meteor strike in the
landlocked Persian Gulf.
     Now note that if the rainbow symbolizes a bow of divine protection, it
faces up, so that the drawn arrow would point toward the sky. So we might
infer that God promised He would never again permit meteorites of such a
size, or in such a quantity, as to cause massive flooding. In the history
books, this is known as the Treaty of Ararat.
    Mt 24.30a also refers to a "sign" of Jesus' coming. This sign is very
likely the rainbow, and this interpretation is reinforced by Ezek 1.28,
where the rainbow surrounds "the Lord," which was probably Matthew's source,
However, Ezek 1.28 implies Gen 9.12-17.
     Lk 21.25c refers to "waves roaring" in the end-times. This prophecy is
not unique, as it can be based on Hagg 2.6 "shake the sea."  It is possible
that the waves roaring could be caused by meteorites hitting the sea,
although the sea shaking seems more like tea sloshing in a cup, and hence
caused by unstable oscillations  of the Earth on it's axis. This should have
been in Alice's Adventures in Wonderland.
     The 'sign of the rainbow' is probably just a story, but if true it does
not guarantee protection from meteorite strikes on land. (Apparently the
contract with Noah was not checked by a lawyer.)
     However, if UFOs have anything to do with invaders from space, then
perhaps the rainbow is a sign of God's military preparedness, and we don't
have to build anything.