Air Raid
Air Attack
noun, verbal noun, の adjective
A sky attack is an air raid / air attack. Tora tora tora!
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
僕が空を見上げると、ちょうど空襲が始まるところだった。
When I looked up at the sky, the air raid was just about to happen.