Thank you Mark for your advice. I must say however that I am somewhat new to odoo and I am still struggling to understand the functionality of the Software. I have activated the dropshipping in the Settings, but somehow I am still not getting the automated generation of purchase orders from the sales orders nor the sales invoices.

I am trying to setup odoo for invoicing airline tickets to our customers so that customer statements can be generated from within odoo. We are a travel agent and the products (Airline tickets) are "shipped" directly from our supplier IATA,  through the GSD -the Amadeus Selling Platform, to the Customer. The shipped products, the airline tickets transactions, are billed by IATA directly to us.

So there is no physical product that is shipped by us to the customer.

Please advise!.... 

Would the product then be shipped directly from the supplier?  If so drop shipping is what you are looking to do and there is a module that will enable this functionality for you.  The module is named stock_dropshipping in Odoo 8.