disclosed is a method of making aluminum base alloy flat rolled product substantially free of luder &# 39 ; s lines after stretching , the method comprising the steps of providing a body of a lithium - containing aluminum base alloy and working the body to produce a flat rolled product prior to solution heat treating and quenching . the flat rolled product is preaged for a time and temperature which does not substantially affect mechanical properties but which permits stretching the flat rolled product without formation of luder &# 39 ; s lines . thereafter , the preage flat rolled product is stretched and aged to a condition having a substantially stable level of mechanical properties .