I noticed this article on BBC News today about an incident on Saturday 28th in London, England.Do any of the FS airplanes and ATC simulate warning systems if aircraft approach too close? Maybe some payware?Maybe FSX could provide this?http://www.lisav.co.uk/1.jpgHeres an extract of the article:"In the picture, they look like they are close together but it doesn't mean they are. And in fact they were not," he said. "If there had been any incident of them being close together, there are all sorts of systems which would have gone off, both in the plane itself and at air traffic control - but there wasn't any report of an incident." Link to full story here: http://news.bbc.co.uk/1/hi/uk/4660644.stm

Complete BS - that's what minimum or slightly more than minimum vertical separation looks like through a telephoto lens. Look at the relative sizes of the planes - that's a 777-300 on top and an A300 on the bottom - the 777 is a far larger plane, yet they look almost the same size here. The 777 is clearly up higher, which makes it look like it's a similar size.

Does FS have these warning systems built into the sim?

Only if you get some payware aircraft with built in TCAS.