A few years ago (in 2005 I think I was) when I was flying from Gatwick to DTW, I remember 3 different types of security stuff. At the check in counter, the usual questions: did you pack own bag, etc. Then the normal security check pre-liquid restrictions etc with no need to take off shoes. Finally, at the gate, there were 2 male & 2 female set up at tables. Males in one line, females in another. Carry-on bags, personal items (purses, coats, etc), shoes removed & checked, and a quick pat down was done before boarding of the plane done quickly & efficiently. I've not had to deal with the last level of security flying internationally the last few times.