Indeed a style problem. I did a style update from the OSM Carto repository to fix another problem (tertiary/unclassified highways displayed above primary ones, as can be seen here:
http://opengeofiction.net/#map=17/18.55050/89.57341). Now that I have rolled it back, the runways are visible again.
Discussion
Comment from Boge on 1 September 2014 at 02:18
In ‘histor style’ they are both visible. Maybe there’s a problem in the map-style.
Comment from thilo on 1 September 2014 at 19:38
Indeed a style problem. I did a style update from the OSM Carto repository to fix another problem (tertiary/unclassified highways displayed above primary ones, as can be seen here: http://opengeofiction.net/#map=17/18.55050/89.57341). Now that I have rolled it back, the runways are visible again.