Moderator: OpenTTD Developers
Also, when upgrading airports, it's annoying when you have to do a bit of landscaping to fit a bigger airport in and all the aircraft which used to land there now have "void orders" and have to be tracked down and manually fixed one by one. It would be helpful if they just skipped the void order, made a notation which says (void order) beside it, and then checked every time it came to it whether it was still a void order.
when upgrading airports, you can place them with CTRL+click, and make sure to reuse the old station sign, then all orders are kept intact.
As for airports, the problem is if you take too long setting up the new airport, all the planes with that airport in their orders switch to VOID ORDER. This can happen when converting from a small to a large airport, for example, when you have to demolish a building or two to make the larger airport fit and suddenly the local authority hates you. By the time you placate them by planting a forest so you can put down the new airport, all your planes now have VOID ORDERs and you have to manually fix every single one.
1) Prepare the terrain for the new airport before demolishing the old. Flatten the land required. Buy any tiles that have a risk of someone else (town or competitor) building on it.
2) If playing singleplayer, use the Pause function. By default you can use the F1 or the Pause key to toggle pause, that lets you pause/unpause the game with one hand while you switch tools and move the mouse cursor into position with the other hand. Or you can change the "When paused allow" setting to allow you to build while in pause mode.
3) Build another station that links with the airport, so the station sign doesn't disappear. Just make sure to build the new airport so it links with that same station again.
4) Use shared orders. When you have many vehicles (e.g. aircraft) doing the same route have them share their orders list, that way you only have to change/fix their orders once if they become wrong. You share orders by holding the Ctrl key while clicking on the vehicle you want to share orders from. Or even easier, build the first vehicle in depot, set up its orders before starting it, then clone-copy the vehicle (hold Ctrl while cloning it) and the clone will have shared orders.
5) When you need to click a vehicle with the Go to button making orders, you don't have to click it in the landscape view, you can also click it in a vehicle list window.
Remember it takes a full month (30 days) for a station sign to disappear, so if you just prepare you have plenty of time to get the new airport placed down.