<unk> <unk> <unk> <unk> <unk>  Passage: In the early 1990s, Gulfstream Aerospace and the Sukhoi Design Bureau began a joint effort to develop a supersonic small business jet, code named the S-21. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️  Question: What was the jet both companies created together?
S-21