just before that mid-air collision last week. According to this article, the Tu-154's TCAS system told them to climb but the air traffic controller ordered them to descend as revealed by the cockpit voice recorders. German controllers tried to warn the Swiss but the only phone line into the Swiss center was busy at the time.

This doesn't look very good for the Swiss ATC system. However, as tragic as this accident was, it helps to remember how many million flights are made each year around the world without incident, largely due to the hard work of air traffic controllers. It's an extremely demanding job.