Don’t expect the U.S. Air Force to share too much intel about its new stealth bomber.

That, at least, seems to be the message coming from senior leaders, who intend to strike a balance between talking openly about the acquisition effort — the Pentagon’s biggest since the F-35 program kicked off in the 1990s — and guarding details about the technology.

Lt. Gen. Arnold Bunch, the Air Force’s military deputy for the Office of the Assistant Secretary for Acquisition at the Pentagon, said the service made a mistake by being so tight-lipped on the B-2 Spirit program and doesn’t want to repeat those mistakes with the B-21 Raider, currently being developed as part of the Long Range Strike Bomber, or LRS-B, program.

“One of the things we did find out on the B-2 was we weren’t open enough,” Bunch told reports after speaking at an Air Force Association breakfast outside Washington, D.C. on Thursday.

He didn’t elaborate, so it wasn’t exactly clear what lessons the service learned from the lack of transparency.

The B-2, conceived under the Advanced Technology Bomber, or ATB, in the late 1970s saw a series of redesign work that delayed the program by more than two years and cost taxpayers millions more dollars during production. The stealth bomber, made by Northrop Grumman Corp., was first publicly displayed on Nov. 22, 1988.

This time around with the B-21, also being developed by Northrop and nicknamed the Raider in honor of the Doolittle Raiders, the Air Force wants to do things differently but not necessarily tip its hand, Bunch said.

“We have to do better, but we can’t go too far,” he said.

Bunch continued, “Take my willingness to be open. [But] with where we’re at today, I don’t see releasing anymore details for a period of time. We’ve been very open so far.”

“It’s a balance. A balance of transparency so that people understand what we’re trying to do with making sure we don’t release too much information so that potential adversaries could get an advantage,” he said.

Officials are conveying the program’s planned milestones and schedule of events to lawmakers on congressional defense committees, Bunch said. In addition, they provide monthly updates to Air Force Chief of Staff Gen. David Goldfein and Acting Secretary Lisa Disbrow, he said.

“We’re progressing, we’re going into detail and design of the program, and were proceeding along [with] the schedule that we’ve laid out,” Bunch said.

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The program recently completed a three-day preliminary design review, or PDR, Bunch said. What’s more, the effort finished the so-called integrated baseline review that established a schedule for managing both prime and subcontractors “so we’re all operating on at the same schedule,” he said.

“We went into a great deal of detail to make sure … all those linkages work,” he said, referring to cooperation between the service and industry partners.

During a House Armed Services Committee on nuclear deterrence earlier this month, Air Force Vice Chief of Staff Gen. Stephen Wilson first disclosed publicly the bomber recently completed the PDR and was pleased with the progress of the program.

In that same hearing, the head of U.S. Strategic Command, Gen. John Hyten, said he was not fond of seeing press coverage of covert or strategic programs in development — even basic information like cost.

“I hate the stuff that shows up in the press,” Hyten said of preliminary numbers. “If you put a cost estimate out in the press, it’s not only our adversaries that are looking at it, but the people that are going to build the system are looking at that.”

Northrop in October 2015 beat out Boeing Co., the world’s largest aerospace company, and Lockheed Martin Corp., the world’s largest defense contractor, for the $21.4 billion initial contract as part of the LRS-B program. The effort could eventually cost more than double that figure.

The Air Force’s preliminary photos of the mock-up have critics grumbling that the future bomber closely resembles the B-2.

The service plans to buy 100 of the new bombers — at an estimated $550 million per aircraft in 2010 dollars — to eventually replace its fleet of B-52 Stratofortresses and a portion of its fleet of B-1 Lancers.

Bunch said the “next thing we’ll probably have is a critical design review” but — perhaps not surprisingly — did not give a timeline of when that would begin and or when it would be completed.