You can learn a surprising amount about a secret aeroplane from the buildings people put up for it.

On 10 September 2026, the US Army Corps of Engineers awarded Conti Federal Services a $74.8 million contract to build a radio frequency and measurements hangar for the B-21 Raider at Whiteman Air Force Base, Missouri. One aircraft bay, some workshops, material storage, offices. Three companies bid. The work is due to finish on 25 September 2029.

The unglamorous part of that sentence is the important one. A radio frequency and measurements hangar is where you park a stealth bomber and find out how invisible it actually still is.

Why a stealth bomber needs its own measuring room

Low observability is not a property an aircraft has. It is a property an aircraft has today, in this configuration, with these panels fitted, these coatings intact and these access doors correctly closed. Every removed panel, every repaired coating, every replaced antenna moves the number, and the number is the whole point of the aeroplane.

So a stealth fleet needs somewhere to check. A radio frequency and measurements facility is an electromagnetically controlled hangar in which the aircraft's radar signature and its electronic systems can be measured without the outside world getting in the way. It is the stealth equivalent of a weighbridge, and without it a maintenance unit is guessing.

Conti Federal has form here. The company has built several other B-21 support facilities at Ellsworth Air Force Base in South Dakota, including a $31.7 million fuel cell maintenance hangar awarded in October 2024, as part of a multi-year construction programme running alongside the bomber's introduction.

Whiteman is becoming the hinge of the bomber force

Whiteman was selected as the B-21's second main operating base, chosen ahead of Dyess Air Force Base in Texas. Ellsworth was picked first, back in 2021, and now serves as the formal training site. Air Force leadership visited Ellsworth in July 2026 to mark what the service described as a milestone in that base's B-21 facilities work.

What makes Whiteman different is that it is already a stealth base. It hosts the Air Force's entire fleet of B-2 Spirit bombers, along with the maintenance culture, the security architecture and the specialist trades that a low-observable aircraft requires. Building B-21 infrastructure there is cheaper and faster than building it anywhere that has never done this before.

For a while, Whiteman will be running two generations of stealth bomber side by side, which has not happened before and is going to be one of the more interesting maintenance problems in the Air Force.

Concrete is the honest programme metric

Aircraft programmes generate a great deal of optimistic language and comparatively little verifiable fact. Military construction contracts are different. They are competed, they are priced, they have completion dates, and somebody has to pour the concrete.

A signature-measurement hangar with a 2029 completion date at the second operating base tells you the Air Force expects B-21s to be at Whiteman in numbers, needing regular signature checks, before the end of the decade. The B-21 is intended to replace both the B-2 and the B-1 Lancer, with B-1 retirements expected to begin around 2031 and 2032, leaving a two-type bomber force alongside the B-52.

Nobody spends $74.8 million on a building to measure an aircraft that is not coming.

Sources: US Army Corps of Engineers contract announcement via Defence Blog; U.S. Air Force; Air & Space Forces Magazine; AeroTime.