Also, warrant officers holding the rank of Chief Warrant Officer (CWO) are to be addressed as “sir” by other ranks. Since all warrant officers are non-commissioned officers, they are not saluted.

Do you have to salute a warrant officer?

All military enlisted personnel in uniform are required to salute when they meet and recognize a commissioned or warrant officer, except when it is inappropriate or impractical (for example, if you're carrying something using both hands). A salute also is rendered: ... To officers of friendly foreign countries.

How do you address a CWO?

Civilians can address them as Chief Warrant Officer or CWO or Mr/Mrs/Miss/Ms (followed by surname).