Let's take this roleplay to the next level!
RULES:
1. It has to be certifiable by the world's international aircraft design standards if you want to be able to sell your airplanes to countries that follow them!
Refer to these guidelines for aircraft design:
Aircraft Classification to determine the general dimensions of the aircraft
Doors and Exits Standards to determine the size/location of doors which will relate to passenger capacity of the aircraft
Unit Load Device for those would be cargo airplane makers
There are many more standards from FAA (Transport Category Airplanes), IATA, and EASA, CAAC, SCAA and many other administrative bodies per country.
Don't be overwhelmed, just observe the basics, and common sense.
2. Provide a template! It can be a simple line drawing. No template, your program will be ignored. The template means your aircraft is in production.
3. For your aircraft to be considered sold to a customer, the customer should have their livery painted on the template. To order an aircraft, have it painted in your livery.
4. Provide general specifications (length, wingspan, design weights, performance, and propulsion specifications).
Extra (optional) notes to make this place more fun and colorful:
1. Provide seat maps if possible (typical configurations or customer specific)
2. Technical drawings like 3-views and structural diagrams will make your airplane more real.
3. You're not limited to passenger aircraft. Design military, bizjets and multirole craft!
4. You can use real world parts suppliers (engines, avionics, interior) or your own.
ENJOY!