Steve/Natasha.
It's not as though we have the rest of SHIELD's supply of quinjets available. Given how many HYDRA took with them, I'm glad he tucked a few away. But now is when they're needed.
Our worlds are related, but we're not a copy. We're not the same people. We don't have the same relationships, experiences, and situations. Even should our situations be similar, I may not make the same decision as their Natasha, or you the same as their Steve. I think of it more like the Many Worlds theory in physics. Many decisions in the past were the same or similar as theirs, and so some of the situations that come to be now are similar. But our worlds were not the same before. And they certainly aren't the same now. Our world isn't even the same as it would have been, had they not come through the tesseract. Nothing is set in stone. It may have been sketched, but the final work is up to us.