Though there were airfields in Shropshire during the First World War, at Shawbury, Tern Hill and Monkmoor, it was in the late 1930s that a massive building programme began to dot the county with new RAF airfields, mostly for training purposes, until there were over sixteen - in some cases they were so close together that their circuits overlapped. Since the Second World War the number has fallen away, but Shawbury, Tern Hill, Cosford and little Chetwynd are still used by the RAF, and Sleap has been revived for general aviation. In most cases the others have returned to agriculture and a few to industry, with derelict control towers and other iconic buildings remaining as lost sentinels of the days when young men trained to carry the fight into the dark skies of Germany.