Money. When one of the 47 pilots looked at the cost of the foam in 2001 it was $25,000, per ac. When Liam Fox wrote to LM in January they were quoted £50,000 per ac. The actual cost is considerably higher than that. Lets say £600,000 per ac, which is the highest Govt quote I have seen. Last time I checked 3 days ago the cost of a brand new J Herc was £50 million. Lets ignore the cost of human life for a second. The whole fleet at Lyneham could be fitted out twice over for the cost of one ac. Does it make sense to you now? Compare it to the price of a sexy new DAS and it is piffling. Remember for the USAF this is baseline protection on which every other type of defensive measure is built. This is no longer an optional extra, this is a basic requirement.