WASHINGTON — When the Pentagon sends its annual budget request to Congress, it traditionally comes with five year's worth of numbers, projections known as the Future Years Defense Program, or FYDP.

It's a key tool for those who want to know how a program is slated to grow. Want to see what the spend on F-35 jets will be in the next few years? Consult the FYDP. Those numbers change year by year, but provide a broad sense of where the budget may grow or shrink in the future.  

But this year's budget, the first under the Trump administration, is different. In some cases, there are no FYDP numbers. In other cases, those numbers are essentially placeholder figures that the Pentagon's top budget expert says should, essentially, be ignored.

For full FY18 budget coverage, click here.

John Roth, the acting comptroller and chief financial officer, told reporters at a budget rollout event that "what OMB has provided to date for the Defense Department is a flat top line beyond FY18, which is simply the FY18 number that is extrapolated and inflated across the out years. That is not the top line that we will be seeking here particularly as we go to the FY19 budget."

The reason for doing so is twofold. One is practical — the new administration spent so much time at the start of the year trying to get the FY17 budget amended and settled with Congress that it had limited time to deal with the FY18 budget.

The other reason is strategic. The Defense Department is undergoing a series of major reviews, including the new National Security Strategy, which will guide future spending patterns of the Pentagon. Until those reports are done, DoD planners would just be guessing about what is to come in the future.

"That flat line is not informed by strategy and it's not informed by policy," Roth said. "So I actually feel that any analysis or any comparisons of what is that out-year profile now is a relatively empty exercise. Because one of the standard answers are going to be, we're going to have to go back and look at that this fall.

"You will not see a growth in force structure. You will not see a growth in the shipbuilding plan. You will not see a robust modernization program in the so-called current FYDP. And so therefore I caution anybody from trying to make any comparisons. And I'm actually of the school that providing it doesn't provide anything that is particularly insightful."

Todd Harrison, a budgetary expert with the Center for Strategic and International Studies, says "It is not completely unprecedented to withhold the FYDP," noting that the Obama administration’s first budget did not include a "detailed FYDP" either.

He acknowledged that program data has been released with the FYDP attached, but warned against reading too much into it.

"The fact that some FYDP data was released but OSD says it is subject to change means that the plans shown in the FYDP do not necessarily have the backing of the new administration," Harrison said. "With that said, it is the best data available for understanding the future trajectory of specific programs so it is certain to be analyzed by Congress, industry, and others."

At least one influential member of Congress — Rep. Adam Smith, the ranking Democrat on the House Armed Services Committee — expressed concern Wednesday about the state of the FYDP.

"I am seriously disappointed that President Trump's defense budget omits long-term planning assumptions that are needed to make sober and strategic choices about national security," Smith said in a statement. "It impacts the military's ability to respond to current and future threats when you don't include this future planning information in your defense budget. These things matter. As we mark up this year's defense authorization bill, those gaps will have a negative impact on our ability to get the Defense Department what it needs."