In December 2016, an E-2D flew for the first time fitted with an aerial refueling capability. This feature will allow the aircraft to double its time on station to five hours and increase total mission time from four to seven hours. The refueling modification will start being built into the 46th plane (out of 75 planned) for delivery in late 2020 costing an additional $2 million per aircraft and the Navy plans to retrofit the feature on all previous Hawkeyes for $6 million per plane.