Before detailing the value of non-destructive testing in the aircraft industry, it seems best to explain aircraft structural design philosophies as they affect NDT.

Airworthiness and weight-saving are two over-riding factors in aircraft design. The important parameter from an economic standpoint is the weight. Fig. 1 shows the value of weight saving for a civil aircraft operator in £ per lb with typical values going up to £100 per lb per aircraft per year. (This figure shows the actual financial saving associated with the reduction in operating economics due to the lower weight.) But the vulnerability of an aeroplane in any failure case makes safety a paramount consideration. To save weight, design factors on aircraft are very low.