Keywords: aviation aircraft airplane experimental flight experimentalflight flight test flighttest military aviation militaryaviation naval aviation navalaviation united states navy unitedstatesnavy us navy usnavy usn bell aircraft bellaircraft bell bell l-39 belll39 l-39 l39 l-39-1 l391 allison allison v-1710 allisonv1710 v-1710 v1710 v-1710-117 v1710117 blackandwhite monochrome outdoor black and white Bell L-39 Experimental Aircraft Showing wing sweep (Approx. 30 degrees) and 80% slats extended Bell L-39 Experimental Aircraft Showing wing sweep (Approx. 30 degrees) and 80% slats extended |