The US Air Force has released to industry a draft copy of a document soliciting bids for a $6 billion plan to acquire 17 aircraft to replace the Boeing 707-based, Northrop Grumman E-8C JSTARS ground surveillance fleet.

The eagerly anticipated release allows the three bidding teams — Boeing, Lockheed Martin and Northrop, along with suppliers — to review and comment on the air force’s proposed terms for the competition.

In a short summary released publicly, the air force says the draft solicitation covers an unusually extended timespan, asking bidders to submit detailed pricing for the engineering and manufacturing development phase, low-rate initial production and the first three lots of full-rate production.

The final RfP will be released after a "coordination process" is completed, the air force says.

The air force has expressed interest in a “business jet-sized” aircraft, which has invited candidates ranging from Gulfstream and Bombardier’s largest business jets currently in production to the 737-derived Boeing Business Jet.

In a recent white paper published by the Air Force Association’s Mitchell Institute, however, the former head of the air force’s requirements office for intelligence, surveillance and reconnaissance, retired Lt Gen David Deptula, argues that the JSTARS Recapitalization effort should avoid putting too much emphasis on the selection of the airframe.

A more challenging task, Deptula writes, is making sure the new aircraft can participate in a battlefield network, receiving data from off-board sensors as well as disseminating information from its own sensors and processed intelligence from an onboard battle management team.

Replacing the current JSTARS’ primary sensor — Northrop’s 7.3m-long APY-7 synthetic aperture radar and ground moving target indication (SAR/GMTI) — is also hotly contested in the competition.

Raytheon has proposed a derivative of the active-array APS-154 advanced airborne sensor (AAS) in development for the US Navy’s Boeing P-8A Poseidon. Northrop has not revealed details of its radar proposal, but jointly developed with Raytheon the multi-platform radar technology insertion programme (MP-RTIP) sensor for the Northrop RQ-4B Block 40 Global Hawk and multi-function active sensor (MFAS) for the MQ-4C Triton.