Dovetail Games should add its the full SDK to its Steam version of FSX.

FSX Steam edition is an enhanced version of Microsoft's Flight Simulator Gold, except for one tiny problem, its missing the majority of its sdk/software development kit files to use in scenery making, mission making as well as aircraft creation/addons, we need enough signatures to get the word out about this game, I am a flight simmer myself and had the original boxed version of this game myself, but I cannot afford the boxed version no longer due to skyrocketed prices, a new unopened version of FSX Gold is $190.00 to $280.00 at the most, and if a person settles for a used second handed copy, they will regret it, like I did and am still waiting for an approval from a seller from Amazon, these used discs are badly damaged and have scratches in a circular pattern.