Air cover and Umbrella

Air cover noun - The use of military aircraft to provide protection against attack by enemy aircraft during ground or naval operations.

Umbrella and air cover are semantically related. In some cases you can replace term "Umbrella" with "Air cover", this terms are similar.

Umbrella noun - A lightweight handheld collapsible canopy.

Air cover and umbrella are semantically related. Sometimes you can replace phrase "Air cover" with "Umbrella", this terms are similar.