It certainly used to be practiced. My last flight, in the 52nd week at Pleiku was to fly up the valley north of Dak To, just south of the Dak Sut Special Forces camp, and retrieve a data plate from the ship I had left on fire the day prior ( a whole other story ) and this was the reason I was given: there was a business in using UH-1 data plates and building a new machine around the data plate.