I notice that, after using the AFCAD2 programme to make some small change to an airfield/s AFCAD file and then saving the change, that I finish up with 2 AFCAD files for that airfield -- the default one and the MOD one. Is this a problem? Should I delete the default one?Barry

no problem, you can't delete the default AFCADfils as they are part of the scnery, i actually have another set of AFCAD files below the originals for renamed airports.

The default and the MOD entry are normal. It's having two MOD entires which is a problem.AFCAD only modifies about 65-70% of the data in the base file necessary for the airport to work.The rest of the data has to come from the default APnnnnn.BGL file.But FS is very smart - it can read from more than one file and give your a final airport with the highest level change for each. Some buildings are in the airport APnnnnn.bgl file - and some are on other files - just as an example. VOR and NDB information is not even the airport files.FS can also understand if you install an add-on scenery which covers only part of the airport. The part of any airport covered by an add-on scenery will not display the taxiways and aprons from either the default or the add-on AFCAD file. But those areas of the airport not covered by the scenery will get their visual elements from the AFCAD data.Either way the AI parking and taxi information will be from the add-on AFCAD.There are a couple other scenery design programs which can create AFCAD type airport information for AI and user aircraft. Files created for those sceneries cannot be edited with AFCAD to change taxi routes or parking - LPPT & KPSP by two different designers to name two.Also - never remove or modify the default APnnnnn.bgl file - it can contain up to 300 different airports in the one file.