Best way to make a huge terrain for flight simulator?

As the topic states - I’m making a flight-based game and I need a way to create a huuuuuge terrain for the ground. What is the best way to do this, performance-wise?

Robert Oats gave a talk at Unite 2013 that discusses some of the issues with large terrain databases. Creating a system to stream in / out terrain in tiles (perhaps even multiple resolutions), and keeping the camera near the origin to maximize floating point precision (by moving the world rather than moving the camera) seem to be good suggestions. I’ve never implemented such a system by hand. but it’s not trivial.