Near the end of Avengers: Age of Ultron:
Nick Fury: One of our tech boys flagged this. Splashed down in the Banda Sea. Could be the Quinjet. But with Stark's stealth tech, we still can't track the damn thing.
Natasha Romanoff: Right.
Nick Fury: Probably jumped out and swam to Fiji. He'll send a postcard.
Which Stark was she referring to? Maybe she meant Stark Industries, but do we have enough data to infer which Stark actually developed (or was involved in the development of) that stealth tech: Tony Stark or Howard Stark?