Thank you, Carlos and willygoat. Now, I'm proceeding to the build report.
1. Cut out the cabin from the plan and cautiously cut out the door using a sharp blade or cutter. Trace the door on waste paper of the same weight as a template. Cut out the template slightly about 5-8mm in perimeter larger than the door. Use this template to glue under the position of door on the cabin plan. Colour the edge of the cabin plan where the door is and colour the template along the edge mentioned above to approx 5mm wide. Then cut out the uncoloured part of the template. Repeat on the other side.
2. Now glue the doors to their original position. The template now acts as a tab on which the door can be affixed squarely. Don't apply too much glue (PVA I would suggest) and there you have a cabin completed. Of course, if you would explore building seats, control sticks and panel etc in there, you can leave the doors open for now.
This is the way I did it as it is quite impossible to glue up the whole cabin without sticking your finger or similar equipment, like a chopstick or a rod, to press down the tabs inside. The cabin has double curves on both sides to crease and assemble and glue, that's why my way of doing it would be a better way out. If you guys can suggest another way, you're welcome to let us know.
The pics are self-explanatory and hope I have explained the steps of building the cabin clear enough.
Papermate