A fighter costs tens of millions of dollars, at least. A stand-off missile to keep it and its crew safe from air defenses can cost hundreds of thousands. But a wing kit and guidance package, converting a bomb into a guided glide weapon that might do the same job, probably costs only tens of thousands.

Creating such a weapon by mating a range-extending wing to the Boeing Joint Direct Attack Munition (JDAM) guidance unit is such an obvious idea it is surprising that the concept is only now going into production, as JDAM-ER (extended range). Boeing says it aims to begin deliveries of an Australian-developed wing kit in 2015, with the Royal Australian Air Force (RAAF) as the first user.

The range of JDAM-ER is classified and depends on the launch conditions and commanded trajectory, but data from a predecessor program suggests that 110 km (60 nm) from high altitude is likely, presenting a considerable challenge to air defenses. Stand-off weapons are already hard to handle, but what if the enemy has 10 times as many?

Glide bombs have well-known limitations, however. The launch aircraft must expose itself by flying high if the bomb is to go far, and the weapon's sedate gliding speed gives alert defenders a long time for reaction. Historically, a further problem for such weapons has been the high cost of the guidance system, but that changed in the 1990s with the arrival of the mass-produced JDAM unit using GPS and inertial data.

Despite its obviously wide applications, the JDAM-ER program has received little attention. Its existence has not been secret—indeed, it roots go back to an Australian development effort that began in the 1980s—but until now the Australians and Boeing have said little about it.

Australia contracted Boeing last year to build and integrate the wing kits based on a design by the Australian defense department's Defense Science & Technology Organization, which also took part in further development. Boeing is working with local manufacturers to initiate production.

The kits will be first used on Boeing Hornet and Super Hornet fighters of the RAAF, but the market is obviously much wider. “The wing kit does not significantly increase the weapon's mass or size, so JDAM-ER can potentially be used with any platform that carries JDAM,” says an Australian defense official. According to a Boeing executive in Australia, Bill Profilet, several countries have already expressed keen interest in buying the wing kit.

One country that has a clear need for cheap stand-off weapons, South Korea, is not a likely buyer. In 2009, Boeing and manufacturer Times Aerospace Korea began co-development of a wing kit for 2,000-lb. JDAM bombs. The two companies have ended their agreement, but Boeing aims to complete the work with other partners.

Like the JDAM guidance-and-control units, the wing kits will be fitted at air bases, creating JDAM-ERs as required. The simple field-support equipment of JDAM is retained and the winged bomb uses the same interface with the aircraft.

“In one of its land-attack modes, the target coordinates from the mission planning system are transferred to JDAM-ER,” the defense official tells Aviation Week. “In flight, the acceptable launch range is displayed to the pilot. After weapon release, the wings are deployed and JDAM-ER glides to the target following an optimized flight profile. Impact parameters can be commanded to maximize the effectiveness of the bomb.” Those “impact parameters” can presumably include a final steep dive for penetrating hardened or buried targets.

Photographs suggest that the wing kit does nothing but unfold, leaving flight control to the JDAM unit mounted on the tail. Australian defense analyst Carlo Kopp believes JDAM-ER determines its angle of attack inertially, doing without the pressure sensors used on the predecessor Australian glide-bomb project, Kerkanya.

The Australian work is based on the Mk. 82 bomb of 500 lb., but the defense department says the technology can be scaled to different sizes of bombs and to other, unspecified weapons. “There is potential to augment JDAM-ER with low-cost seeker systems to engage ships and moving land-based targets,” it adds.

The wing kit's low cost is a crucial but unspecified feature. The JDAM unit costs about $20,000; Kopp doubts that the wing kit would cost much more. Since it is apparently made mainly of pressed metal, it could well be cheaper, especially if sales are high.

Boeing has said the wing more than triples the range of a JDAM bomb to beyond 64 km. Kerkanya data suggests an ideal maximum range of about 150 km when launched from 9,100 meters (30,000 ft.), but Kopp says 110 km is likely to be a practicable range. The more the bomb turns, the shorter the distance it will fly. The defense department says a JDAM-ER can turn around and attack targets at a “significant range” behind the launch aircraft.

“The extended range provides operational flexibility, such as prosecuting more targets on a single pass and attacking off-axis targets,” the defense department official says. Pilots can toss ballistic bombs to greater range by climbing as the weapons are released, but the official says the technique makes little difference to JDAM-ER, because “the flight profile is optimized to achieve the target range with maximum warhead effect in all cases.” The connection is not clear, and in any case the defense department appears to assume a high-altitude launch, since a glide bomb released near ground level will certainly not go far unless tossed.

Quite apart from the safety of stand-off release, the range of the weapon will usefully extend the reach of Australia's F/A-18F Super Hornets, says Andrew Davies of the Australian Institute of Strategic Studies, noting that the aircraft cannot fly as far as the F-111 strike bombers that they replaced.

The advantages offered by a gliding JDAM keep raising the question: Why has it taken so long to appear? The answer is unknown, though Australia and other countries, including China, have long worked on glide-bomb projects.

Australia's Kerkanya was canceled in the 1990s for lack of funds after successfully demonstrating inertial guidance. It was planned also to incorporate GPS. Companies later bought by Boeing acquired rights to the wing kit, which has since been simplified by eliminating taper, presumably at some moderate cost. It is unclear when the decision was made to drop the Australian guidance system and instead use the JDAM unit, but Kopp privately urged the U.S. Air Force and manufacturers to do exactly that in 1997, writing that persisting with a separate development “strikes me as a case of unnecessary duplication.”

Among the challenges in developing the wing kit was accurate transonic wind-tunnel measurement. Although much of the original electronics work was not used, it promoted expertise that the Defense Science & Technology Organization could use on other projects.