Now that Boeing has achieved the 5/month assembly rate on the 787 program, the challenge is to make sure the higher rate doesn't contribute to the increase in the number of stored 787 at Everett. This backlog is about $20bn worth of WIP inventory on Boeing's balance sheet and they have made great progress in the last couple of months to reduce it.
The key, however, is to make sure that this inventory doesn't increase because of the higher rate. The way to do that is to make sure that 787 deliveries exceed the assembly rate each and every month so that the stored inventory is reduced to 0 (this should happen sometime around the 2nd half of 2014).
This month so far Boeing has delivered 3 787s including one straight from final assembly. Boeing has the potential to deliver 4 more 787s straight from the Everett line (these four are already on the flightline with 2 of the four already having flown) in addition to several frames that went through change incorporation at the EMC. While the challenges remain, delivery rates will again be dependent on Boeing's resources as well as the readiness of certain customers to accept delivery of the frames.