Boeing's aggressive 787 delivery schedule is being threatened by two issues: availability of BFE (buyer furnished equipment) namely the premium seats from Zodiac but more importantly the ability of certain airlines to fund the final payment to Boeing upon delivery. Most of the aircraft's purchase price is paid upon delivery. The seat issue has already shifted several deliveries into January.
For some carriers with less than stellar cashflow, obtaining the financing to fund this final payment has been tough. In particular Avianca and Azerbaijan Airlines have had aircraft that are all set to deliver yet are still sitting on the flightlines at Everett and North Charleston. The delivery dates have been repeatedly moved to the right and there hasn't been any further test flights nor any need for further test flights unless the delays take much longer at which point Boeing would have to fly a FCF (functional check flight) to make sure that the aircraft and it's systems still all check out.
Avianca has 4 787s on the flightline with 3 ready to be delivered. Azerbaijan has both 787s that they ordered ready to be delivered as well. The delays have been driven by the customers and not Boeing yet represents 6 aircraft that could be added to their year end and month end revenue totals. Boeing is trying to keep the delivery schedule for these 6 airplanes in December and it does appear that they have time especially since the issues doesn't appear to be technical.