[As much as Tony doesn't like Loki, he's still keeping his his word to Thor. He won't start a fight if Loki doesn't. A truce right now is better than a fight in unknown territory. Sure, he could probably give Loki a good run for his money with his skills. Even if he's not a god and even without the Avengers to back him up, Tony's greatest advantage is his resourcefulness. He works well under pressure. But he wouldn't get away with that without hurting, and neither of them know what kind of dangers are lying in wait for them to make a dumb misstep. Personal problems are going to have to come second to god-capturing gates and mysterious ships with no crew.]

I'm saying it's better for both of us if you agree to play nice. I'm not thrilled to be stuck on this ship with you, but, yeah, we're stuck. I'd rather find a way out of here than spend time fighting you.

[Or potentially pissing Thor off. Neither of them really like that.]

Let's call it an agreement for the sake of common interest.