The US government has cleared Tokyo to obtain nine additional Northrop Grumman E-2D Advanced Hawkeye airborne early warning & control (AEW&C) aircraft.

The US State Department announced the potential deal in Defense Security Cooperation Agency (DSCA) statement. This means that Tokyo could eventually obtain up to 13 E-2Ds, as it already has firm orders four examples of the type.

The DSCA says the nine aircraft contract could be worth up to $3.1 billion. Tokyo tends to order one aircraft per annum.

Should Tokyo buy the full allotment of E-2Ds, it could replace its aging fleet of E-2Cs on a one-for-one basis. Previously, however, officials have said that the new aircraft will augment rather than replace the legacy E-2Cs.

Flight Fleets Analyzer shows that the Japan Air Self Defense Force operates 13 E-2Cs, aged between 25 to 36 years old.

In addition to the nine aircraft, the package includes 28 Rolls-Royce T56-A-427A engines (18 installed and 10 spares), ten Lockheed Martin APY-9 radars (nine installed and one spare), plus an array of equipment, support, and training.

Japanese E-2Ds have several modifications compared with those operated by the US Navy. Given that the type will operate from land bases, and not aircraft carriers, it is modified to carry extra fuel in a “wet wing”, providing endurance of 8h, compared with 5h for the US E-2Ds. Those aircraft rely on air-to-air refueling to boost their endurance.

In addition to the 13 E-2Cs, Japan has four E-767s serving in the AEW&C mission. The average age of these aircraft is 22.7 years.

The sole operator of the E-2D is the US Navy, which has 31 examples. It has firm orders for an additional 24, and letters of intent for another 24.