It helps to look at it this way: is the actual business activity of getting goods from point A to point B related to the state for any economic or business purpose other than incidentally transiting through the state? (For example, are goods being delivered to customers in that state?) If so, you may but probably do not have a business activity in the state.

With a travel company, the distinction is that the journey is as much a part of the business activity as reaching the destination.