Leeham Co. analyst Scott Hamilton broke the news last night that Delta Airlines has decided to go with Airbus' offer of the A350-900 and A330-900 aircraft essentially rejecting Boeing's offer of the 787. The rumor, right now, is that Airbus offered favorable delivery slots in 2017 while Boeing's delivery book for that year is completely sold out.
Interestingly Delta had inherited Northwest Airlines' 787 order when they merged in 2009. At that point the Delta had the early delivery slots for the 787s yet over time they had elected to move those delivery slots further out to the right to around 2020 and beyond. If they had kept those delivery slots for the 2017-2018 time frame, Delta could have had the 787-9 and at a very competitive price as well. One has to question Delta's fleet management decisions in context of the Airbus order while still holding a 787 order with early delivery slots.
Now that they have gone with Airbus the 787 order is in limbo and, in my opinion, order that will never be delivered even though it will remain on the Boeing order book just like Virgin Atlantic's A380 order with Airbus.