Inheritance relationship in ERD diagrams

ER modeling (or, more precisely, EER modeling) has a way to represent inheritance in the diagram. It goes by the name "generalization/specialization". You can find a number of good articles on the web by searching on this.

The diagramming technique doesn't tell you how to design relational tables that reflect this inheritance situation. That's really more a matter of database design than ER diagramming. If you look up Martin Fowler's treatment of "class table inheritance" or "single table inheritance", you'll get a good presentation of some design patterns.

There are tags with those names here in SO, and the info under those tags is helpful, as well as the questions that have been tagged with them.

inheritance relationship in ERD should be represented as One-To-One relationship or One or Zero-to-One relationship depending on the case.

1) 0..1-1 : If there could be an entity of plane since plane can exist without having child entity like cargo or personal but cargo and personal cannot exist without having a parent plane entity.

2) 1-1: If each entity cannot exist by it self. The PK in plane is the foreign key and primary key in cargo and personal child tables.

I don't think that in any case it is a one-to-many and I will give you an example: a db record of plane pk=1. Two db record of personal plane with foreign key=1 referencing one record in parent plane table. This means that there are two children entities with same key which is wrong. There must be only one referenced record in the child table thus 0..1-1 or 1-1 relationship.