So it seems that when you order planes and get your production slots assigned, the system doesn't offer you the earliest available slots. It offers you the earliest available slots after the slots you're already occupying. You also don't have the option to move your current slots to the earlier open slots.
For example. I order two 767s scheduled to arrive 2 years from now as those are the earliest available production slots. Something happens and more slots open up before 2 years. I go to order more 767s however I am assigned slots 2 and half years from now even though there are slots available a year from now. Is this a bug or intended mechanic?