Alt host in multiple meetings

I'm responsible for multiple meetings occurring at the same time. Each meeting has a host, but I need to pop in to each meeting to check on things and sometimes I need to start a meeting for the host. The other day I was in a meeting as an alt-host, I left the meeting so I could join another one and I was not able to. It said I was still in the other meeting and could not join unless I ended the other meeting. That was a problem because I needed to start the other meeting.  My question how can I be alt host and jump from meeting to meeting. I will only be in one meeting at a time. I will not have multiple meetings open at the same time.