Wiktionary
n. In a war, the most favorable state of control of the air. It is defined by NATO and the United States Department of Defense as "that degree of air superiority wherein the opposing air force is incapable of effective interference."
Wikipedia
Usage examples of "air supremacy".
They've got air superiority now and they could have air supremacy in a few more days, but a determined offensive by the RNAF or even a spell of nasty weather could cut those troops off with virtually no supplies.
The Wasps had long since died out, and I wanted to take advantage of the air supremacy that we had fought so hard for.
If you Jao hadn't had air supremacy, things would have turned out very different.
In consequence, around these vital installations they had numerical superiority, immense air supremacy and an overwhelming balance of fire-power.
Thanks to the previous defeat of the British Air Force by the invincible Luftwaffe, air supremacy was maintained at all times.
In theory, if they could knock out the cannon and if the other forces were equally successful, the government troops could regain air supremacy.