This will demonstrate the key setups to allow Internal Orders to be created successfully with correct Scheduled Ship Date and Arrival Date, showing the offset of the transit time. The Need By Date on the Internal Requisition should be the Arrival Date for the Internal Sales Order.
Additionally, starting in 11.5.10 with the new calendar functionality, we have related articles to help manage this functionality with specific calendars controlling when orders are shipping, transited and received.
Internal orders - intransit lead times setup steps 2011-04-12
Internal orders - intransit lead times setup steps