one submarine in each of fiscal 2009 and 2010, and two submarines on each of fiscal 2011, 2012, and 2013. This contract was designed to bring the Navy's Virginia-class fleet to 18 submarines. In December 2010, the United States Congress passed a defense authorization bill that expanded production to two subs per year. Two submarine-per-year production resumed on 2 September 2011 with commencement of construction. On 21 June 2008, the Navy christened , the first Block II submarine. This boat was delivered eight months ahead of schedule and $54 million under budget. Block II boats are built in four sections, compared to the ten sections of the Block I boats. This enables a cost saving of about $300 million per boat, reducing the overall cost to $2 billion per boat and the construction of two new boats per year. Beginning in 2010, new submarines of this class were to have included a software system that can monitor and reduce their electromagnetic signatures when needed. The first full-duration six-month deployment was successfully carried out from 15 October 2009 to 13 April 2010. Authorization of full-rate production and the declaration of full operational capability was achieved five months later. In September 2010, it was found that urethane tiles, applied to the hull to damp internal sound and absorb rather than reflect sonar pulses, were falling off while the subs were at sea. Admiral Kevin McCoy announced that the problems with the Mold-in-Place Special Hull Treatment for the early subs had been fixed in 2011, then Minnesota was built and found to have the same problem. In 2013, just as two-per-year sub construction was supposed to commence, Congress failed to resolve the United States fiscal cliff, forcing the Navy to attempt to "de-obligate" construction funds. In April 2019, the Congressional Research Service (CRS) reported that the Navy estimated the cost of a boat was $2.8 billion. In September 2021, the CRS reported that the Navy estimates at the present production rate of two boats per a year that the cost per a boat when equipped with the additional Virginia Payload Module (VPM) mid-body section was $3.45 billion. Innovations The Virginia class incorporates several innovations not found in previous US submarine classes. Technology barriers Because of the low rate of Virginia production, the Navy entered into a program with DARPA to overcome technology barriers to lower the cost of attack submarines so that more