I don't think AI officially allows that. I know UK has a chargeable scheme for that (free for some elites). It is a wonderful benefit to use in the US.

That said, you could try charming the check-in agent. I once had a BOM-DEL-IAD flight on AI and at check-in the agent proactively asked me if I wanted to take an earlier flight to DEL which would depart shortly. I agreed to it. So they can do it for sure.