First Officer
First officer stands for:
Military:
- Executive officer , first officer in the military command area
- First Officer (German Navy) (IO, sometimes also 1O), the highest officer after the commander and his deputy on board a ship in the German Navy
Civil area:
- Nautical officer #First officer , deputy subordinate to the captain and superior of the other crew members in merchant shipping
- First officer (aviation) , the second pilot on board an aircraft in civil aviation