If Christian Grill doesn’t sound familiar to you, TOPCAT should do. Serious simmers prepare their flight up to passengers, cargo and gross weight calculations for take-off and landing performance speeds reference at least. That’s what the good (old ?) TOPCAT does : even editing sheets, perfect.
The same team is working on Professional Flight Planner X, a tool under development that “can be used with any flight simulator”, will feature NAT / PACOTs routes for transoceanic flights, and will integrate ETOPS/EROPS ! The same software will edit you the Take-Off and Landing performance calculation if you have TOPCAT installed. Read more and see screenshots at http://www.pfpx.com/.