Working on inCopy files offline

Hi, I'm new to inCopy and can't seem to find a solution for this:

The situation: I need to modify a project's text in inCopy files (.indd) while offline, during a very long flight.

Context: The docs are all stored in DropBox.

The ask: How do I check the document out, take my laptop offline, work on the document, and check it back in when I land?

The worry: If I must download the files locally before working on them and a teammate checks the docs out while I'm offline, is there a way to avoid the risk of uploading conflicting documents from two team members? 

Thanks!