Saints Row

You need to go to the actual airport in the Airport District. They wont always be spawned, of course, but I have found a few locations they are usually at. Find the area with the parked plane, facing the plane, head left, a Nightingale can spawn at that little area in front of the garage, or head right, and one can spawn there too. The other place I have found one is next to the control tower building. Some have said destroying the parked plane causes them to spawn, for me, as soon as it became dawn two of them spawned, at the aforementioned areas. I also threw a bunch of pipe bombs once, which apparently caused them to spawn.

- This was taken out of the Chop Shop Guide, which was written by Kresselack.