If it's a choice between a runway extension or the closure of the airport, the obvious answer is a runway extension. BUT - given the apparent success of the backfilling of routes, 'environmentalists' may well question whether the runway extension is actually necessary. Especially if easyJet is already using it successfully for GVA services and potentially could serve BFS/AMS/CDG very easily from SOU if they want to without any runway issues. The runway extension would only benefit outbound package flights to Spain or further afield - in the minds of the environmentalists - how important is a couple of flights a week to Alicante versus the environmental concerns of noise, pollution, carbon targets? I think RW20 raises a good point.