In March 2013, the U.S. Navy was considering the widespread adoption of conformal fuel tanks, which would allow the Super Hornet to carry of additional fuel. Budgetary pressures from the F-35C Lightning II and Pacific region operations were cited as reasons supporting the use of CFTs. Flight testing demonstrated CFTs could slightly reduce drag while expanding the combat range by . The prototype CFT weighed , while production CFTs are expected to weigh . Boeing stated that the CFTs do not add any cruise drag but acknowledged a negative impact imposed on transonic acceleration due to increased wave drag. General Electric's enhanced performance engine (EPE), increasing the F414-GE-400's power output from of thrust per engine, was suggested as a mitigating measure. In 2009, development commenced on several engine improvements, including greater resistance to foreign object damage, reduced fuel burn rate, and potentially increased thrust of up to 20%. In 2014, Boeing revealed a Super Hornet hybrid concept, equipped with the EA-18G Growler's electronic signal detection capabilities to allow for targets engagement using the receiver; the concept did not include the ALQ-99 jamming pod. Growth capabilities could include the addition of a long-range infrared search and track sensor and new air-to-air tracking modes. In 2019, Boeing received a $4 billion contract to deliver 78 Block III Super Hornets for the Navy through fiscal 2021. The Navy plans to sign year to year contracts with Boeing to convert all of its Block II aircraft to Block III variants thru 2033. The Super Hornet is largely a new aircraft at about 20% larger, heavier empty weight, and heavier maximum weight than the original Hornet. The Super Hornet carries 33% more internal fuel, increasing mission range by 41% and endurance by 50% over the "Legacy" Hornet. The empty weight of the Super Hornet is about less than that of the F-14 Tomcat which it replaced, while approaching, but not matching, the F-14's payload and range. As the Super Hornet is significantly heavier than the legacy Hornet, the catapult and arresting systems must be set differently. To aid safe flight operations and prevent confusion in radio calls, the Super Hornet is informally referred to as the "Rhino" to distinguish it from earlier Hornets. (The "Rhino" nickname was previously applied to the McDonnell Douglas F-4 Phantom II, which was retired from the fleet in 1987.) The Super Hornet, unlike the previous Hornet, is designed to be equipped with an aerial refueling system (ARS) or "buddy store" for the refueling of other aircraft, filling the tactical airborne tanker role the Navy had lost with the retirement of the KA-6D and Lockheed S-3B Viking tankers.