I think this might work
http://www.airportdesigneditor.co.uk/
For the lazy people a quote
Airport Design Editor (ADE) is a graphical design tool to create and enhance airports for Microsoft Flight Simulator X. It takes it's inspiration from the excellent AFCAD2 developed for FS9 by Lee Swordy. ADE does for FSX what AFCAD does for FS9 and adds support for new FSX features such as fences and jetways. ADE is being developed with the help of a small group of dedicated airport designers with a wealth of knowledge and experience. ADE sets out to achieve two things in designing and enhancing airports. First to make the enhanced airport look good, and second to make it work properly. Airport design must address both aspects - the visible and the invisible. The design philosophy goes further in assisting users of all levels to get things right from the start. Error checking and 'common sense' are built in. At the same time it is important to allow users flexibility. Airport Design Editor has all the functions that you would expect. For example background images. ADE provides several methods for using images to improve the accuracy of airport design. Multiple images are supported. The image here shows just one example.This website will be developed over the coming months to provide you with the latest on Airport Design Editor. It will also provide a central location for information and tutorials on Airport Design for Microsoft Flight Simulator We are therefore working on two editions. The Home Field Edition for those users who want to enhance their local airport and the Pro Edition for those who want to make more complex enhancements.
Download http://www.scruffyduck.co.uk/files/adeh_100.zip
Hope this helps
-Orion