I trying to create buffers (50km) around many points all over the world (airport locations) in QGIS. I will then overlay these buffers with a world-wide raster dataset so I can extract information from that. The point layer is in WGS84 now, I am wondering what is an appropriate projected coordinate to use (one that does not give me too much distortion)? 

I have searched this site and the internet a lot and did not find an answer because I think this cannot achieved with PostGIS or just by using a projected coordinate system for one country.