Slopping runways must be possible. It has been available in Xplane 9 and maybe even earlier versions. I only have Xplane 9, so thats all I can comment on. the runways simply follow the terrain contour. crossing runways arent a problem, because they cross the terrain at the same point. the only difficulty is that sometimes the terrain contour isn't so accurate, so you end up with a step rather than a slope! Take off is easy one way, but watch the step coming the other way! There is an option to make the runways flat if you prefer, or if those runways cause issues. My problem with Xplane is that there aren't the tools out there to correct the terrain contours easily, so it is difficult to correct those steps at your favourite airport. The amount / smoothness of slope then depends on the level of your terrain complexity. I realise that MS may do things differently, but it can be done, even at complex airports. You dont even need to know the exact details of thresholds etc. there are some great challenges out there, where the slope does add to gameplay. Aerosoft have a number of titles that are developed expressly because their slope creates the challenge. It would be nice though if the sim could support slopping runways without needing third parties to make the product, as there are a number of runways in places like Papua New Guinea that are hugely challenging, but will never get the third party add on treatment. Tapini is an example. In FSX, the airport exists, but instead of being sloped like it is in reality, the airport juts out into the valley like a diving board over a pool. I do hope that MS could do it, as it does add yet another dimension. Just a thought.