As has been suggested, we can offer advice but do not do homework per se.
Please take this initial statement:
My subject is airline reservation. I have 5 kind of aircrafts, some of them are wider (different seat configuration). Can you help me what is the best way to do the seat selection *without plugin.
I want to know which tables I need to do, and which fields.
And flesh it out in simple English to get specific
facts(see below). Use the tried and true who, what, why, when, where, how much and how often line of thought to get a more detailed picture of the assignment.
Database, like other subjects, requires some upfront analysis to understand the issue to be resolved. Think of building a subdivision or a new passenger jet ---shovels, welders etc were NOT step 1. Blueprint based on required functionality, budget... were not after thoughts.
I think this
cinema bookings data model from Barry Williams' site should give you some ideas.
The facts that were used to create that model can be found
here.
We are available to answer specific questions if needed.
There are several articles related to database planning and design at the link in my signature.
Good luck.