This contract might explain activity around HGR and MRB:
"Sierra Nevada Corp., Hagerstown, Maryland, has been awarded a $71,475,750 firm-fixed-price, undefinitized contract action for the Saudi King Air 350 program. Contractor performance includes modification of two King Air 350 extended range (KA350ER) aircraft with intelligence, surveillance, reconnaissance/synthetic aperture radar (ISR/SAR) capability, one transportable ground station, one fixed ground station and one mission system trainer. Work will be performed at Hagerstown, Maryland, and is expected to be complete by April 30, 2020. This contract is 100 percent foreign military sales to Saudi Arabia. This award is the result of a sole-source acquisition. Air Force Life Cycle Management Center, Wright-Patterson Air Force Base, Ohio, is the contracting activity (FA8620-16-C-4003)."