What you can find onboard:

Cockpit with 5 seats
Sleeping rooms for flight staff
Toilets for men & women
First Class cabins
Airline Bar with seats & tables
Private cabins

Other:
In the cockpit, you can find levers that controls lights on the wings and between the cabins.

Recommended resource packs & shaders:

Make the best experience out of this project with this awesome resource pack!

Also, I hardly recommend you to install Sonic Ether's Unbelievable Shaders.
You can find a very good tutorial as well as file links here.