Q.What is the meaning of air draught ?

Air draft - Distance from water line to part of ship that is being considered, usually the highest point.

1. In case of crossing under bridges/wire cables etc - air draft is taken utpo highest point of vessel that is usually the main mast top of bridge.

2. In case of loading - air draft used is the top of hatch coaming (for bulk carriers).

For orals or exams - say distance from waterline to the highest point on vessel.