As part of his farewell tour earlier this year, outgoing Secretary of Defense Chuck Hagel visited Whiteman Air Force Base in Missouri and sung the praises of the Air Force’s planned Long Range Strike Bomber (LRS-B). According to Hagel, the next-generation bomber is vital both for the U.S. military’s planned “pivot” to Asia and as part of the nation’s nuclear triad.

The strategic vitality of the LRS-B is and will remain debatable. Strategic bombing has never been as decisive as air power enthusiasts have claimed. Moreover, while some analysts insist that a long-range, stealthy bomber is essential due to potential adversaries’ possession of advanced air defense, there are reasons to doubt its necessity as part of the nuclear triad.

What is more interesting than Hagel’s commitment to the LRS-B though—notable due to the former senator’s involvement with the nuclear disarmament group Global Zero prior to becoming secretary of defense—is the Air Force’s approach to building it. As Marcus Weisberger at Defense One wrote at the time:

The Air Force has had its eyes set on a new bomber for the past decade. The service had hoped to have a new aircraft battle ready by 2018, but the combination of a tight schedule for building sophisticated, unproven and expensive technology and politics over spending derailed the effort, sending the Air Force back to the drawing board. This time planners pared back expectations, opting instead to build a bomber based on proven technology… using mature technology and systems already used on existing aircraft, something it did not do in the 1980s when building the B-2.

Focusing on existing technology is especially unexpected coming from the Air Force. As Carl Builder explained over two decades ago, among the military services the Air Force has always been the most interested in technology seeing as it owes its existence to a technology—the airplane. It has historically been the service most interested in pushing the technological envelope.

Problems with immature technologies have driven cost growth in a number of recent Pentagon projects. As the Government Accountability Office reported a decade ago, programs based on mature technology remain on schedule, while programs that require immature technology lead to cost overruns. But few weapons will go into development with completely off-the-shelf technology. The Air Force knows this, and that is why the contract it will award this spring to either Northrop Grumman or a Boeing-Lockheed Martin team to develop and produce the LRS-B will be cost-plus. That contract types accounts for the inevitable technological surprises that occur in any development project, but it also helps get a project out of the start gate by putting forward a more palatable initial price tag.

In 2010, Robert Gates placed a limit of $550 million on purchases of the LRS-B. However, it is unclear at this time whether Air Force willingness to base development on proven technology will be enough to keep that limit in place. Moreover, the figure means little at this point. As Mark Thompson explained in Time last month, $550 million is the average procurement unit cost, which has not been adjusted for inflation, leaves out research and development costs, and assumes economies of scale can be achieved by procured between 80 and 100 aircraft.

According to Michael O’Hanlon of the Brookings Institution, major weapon systems tend to exceed initial cost estimates by twenty to fifty percent. It is impossible to know whether the LRS-B will reach those figures, but it is also highly unlikely the price of the new bomber will remain below the Gates’ cap. Even if the Air Force used only mature technology during development, there is no guarantee it will not add complex technological upgrades later that increase its cost over the long term. The LRS-B is certain to experience cost overruns, and it is better that both Congress and the Pentagon know that now if they insist on moving forward with the new bomber