Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Weight And Balance
Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem
Human Factors
During Cruise we received an ACARS message from the company [Dispatch] that they had left 1768kg (initial message said 1768lbs but was later corrected) of Dry Ice off the DG manifest.  We began to send follow up messages back and forth to confirm the location and total quantity of the dry ice.  It was determined that the total quantity was 1884kg vs the DG manifest value of 166kg.  Basically; 2 cans worth of Dry Ice had not be accounted for on the DG manifest.  The crew deployed the Drager CO2 monitoring system immediately and was also directed to do this from the company.  We also ran the QRH for this event.  Upon further review; it was determined by crew and Dispatch that the dry ice quantity on board not only exceeded normal FOM limits; but was over the supplemental limits in the FOM.  I began a conference call with the Dispatcher; DO; and Flight Operations.  Based on all the information; they recommended we deploy the CO2 monitoring system and keep a close eye out for any elevated CO2 levels; but that we should be able to continue safely to our destination which was another 8 or so hours away.  We knew if the levels were elevated we could follow the QRH and use oxygen to breathe safely and divert if needed.  We also knew that we were flying right over ZZZ1 in about an hour which we could just divert to immediately to remedy the problem.  This would give us time to get ready for the divert and allow us to burn enough fuel to get below maximum landing weight.  So basically our options were 1) continue or 2) divert.  We woke up the Captain to provide him all of the data so he could make the decision.  With all the data and the opinions of the crew; he decided we should continue.  The decision was supported by the crew and Dispatch.  The rest of the flight was uneventful.  Obviously; undocumented hazardous materials is a big deal and could have serious safety concerns.  Luckily everything worked out here.  Once the issue was identified; Dispatch was a little slow to get us all the info and to provide input.  I believe this was because the Dispatchers had a shift change.  I think this led to information slowly being provided to all parties. The cause was someone [erred] in the chain of [custody] during loading; documenting; and manifesting must have made an error which led to this dry ice not being manifested.
Approximately 20 minutes into flight; we received a message via ACARS from Dispatch that 1768lbs of dry ice went on the aircraft unmanifested and to please use supplemental dry ice procedures. At that time the RFO was in the jump seat and he retrieved; turned on and distributed a Drager monitor to each crew member. Once established in cruise; CA proceeded to the CRM as planned/briefed and RFO took the left seat. Subsequently we received message that the unmanifested dry ice was 1768kg; not lbs. We confirmed with  that the 1768kg was on the main deck along with the 116kg that was manifested ; for a total of 1884kg of dry ice on the main deck. The main deck limit is 1814kg. DO stated that he and dispatch agreed; that with all systems on the aircraft functioning properly and with FOM 10.37 DRY ICE SUPPLEMENTAL PROCEDURES in place; we were OK to continue to destination; however; if Captain desired to divert that would be appropriate as well given the over-limit situation. At that time; we had just passed the east coast of [State]. Diverting to a [company name] base at that time would have required dumping fuel in order to land under MAXLGW. FO and RFO discussed and determined that we would arrive overhead ZZZ1 on current flight planned route at MAXLGW and that if a divert decision was made; ZZZ1 was the most appropriate divert base. One hour prior to arriving overhead ZZZ1; FO awakened the CA in the CRM and informed him of the situation and [Dispatch's] deferral to him on a divert decision. CA agreed that continuing on  was appropriate. FO/RFO informed [Dispatch] via ACARS of decision to continue to [our destination] using dry ice supplemental procedures. Rest of flight was uneventful. A [contributing] cause was it had something to do with this being a chartered/non standard flight.
Air Carrier flight crew reported Dispatch notification during cruise of incorrect amount of dry ice weight information provided to flight crew at departure.