Info via Reuters:
- As northern Australia re-emerges as a strategically vital Indo-Pacific location amid rising tensions with China, the United States has quietly begun constructing hundreds of millions of dollars' worth of facilities there to support B-52 bombers, F-22 stealth fighters, and refuelling and transport aircraft
- part of a larger effort to distribute U.S. forces around the region and make them less vulnerable.
More at that link above.
Darwin is north of Tindall base. Both mentioned in the article.