Quote Originally Posted by HakuroDK View Post
As for FC transport to the Diadem, it was one Mission Ceruleum tank per airship. I'm 90% sure.
From the patch notes:
Free Company Exploratory Missions
When undertaking exploratory missions using a free company airship, players must form a party of at least two people. Players can also form an alliance of up to twenty-four players. There are no role requirements for entering The Diadem as an alliance. Each party or alliance member must have a tank of mission ceruleum in their possession, which can be purchased in exchange for company credits. One tank is required for each mission
Each person needs a tank of mission ceruleum.