In the summer of 2012, FedEx converted the Memphis to Rochester flight from a 727 to a larger, more fuel-efficient 757 that is sealed tighter to minimize leaks. However, while more efficient, a tighter sealed aircraft results in less air exchange. The exchange rate of air in the cabin is one of the key determinants of how much dry ice the aircraft can carry.
By spring of 2013, growth in Mayo volumes from MML and Mayo Foundation had exceeded the dry ice capacity of the Rochester flight. Because of this, FedEx had to divert MML dry ice shipments from Rochester to Minneapolis to keep it within legal limits. This resulted in delivery delays up to three hours.
In an effort to resume direct operations, MML challenged FedEx to find a solution to accommodate continued growth at Mayo. FedEx responded with a plan to reconfigure its entire fleet of 757s to add 600 kg more dry ice capacity per flight. FedEx pursued approval of its plan through Boeing, and the proposal was presented to the Federal Aviation Administration (FAA).
Boeing received a favorable verbal response from the FAA, and FedEx focused on the internal aspect, updating SOPs and negotiating with the Airline Pilots Association (ALPA) to agree that the additional capacity was safe and acceptable for carriage. However, in October, the FAA was shut down along with the rest of the Federal Government and could not provide a formal approval. FedEx diverted more MML dry ice shipments in October than any other month. MML also had to divert shipments from FedEx to AirNet, Delta, and American Airlines, based on which markets had alternate flights available without changing client pickup times.
By Nov. 21, Boeing had received the formal approval from the FAA, FedEx had agreement from the ALPA to carry more dry ice, SOPs had been updated and weight and balance hardware was updated. On Monday Nov. 25, dry ice capacity on the 757s was increased.
Diversions to Minneapolis have been eliminated, and MML has returned diverted shipments to FedEx.