I've been able to get 3 in the Sparrow. I have 303 Shadowy and Employ Stealth works for me at 100% until I get to 63 Far Afield when Aerial Prowess starts to drop (98%). At 66, the Shadowy challenge becomes 99% (Aerial Prowess drops to 96%). @69 FA, AP is 95%, Sh 96%; @72 FA, AP 93%, Sh 93%; @75 FA, AP 92%, Sh 90%; @78 FA, AP 90%, Sh 88%.

If you fail, you'll still get some FA, but then you get attacked. At that point are some very difficult challenges. Not sure the mechanics of the attacks. You can still make some FA progress without taking up fuel if you fail, but you'll start to build up damage very quickly. I've been lucky enough that I've still been able get to the 3rd landmark without crashing/dying.

At the end of my last perfect run for 3 landmarks, I got 1863 x Survey of the Neath's Roof and the hand in nets me 22380 x Service to London.