The Air Force now expects the cost of the GPS III ground control system (OCX) to reach $5.5 billion, spokeswoman Capt. Annmarie Annicelli said in an email statement. That amount may change in June when the service releases updated cost estimates for the milestone B review. Annicelli also said the service had spent $3.6 billion on the program so far. President Donald Trump’s fiscal year 2018 budget proposes $511 million in new spending on the program. At a space budget briefing on May 24, Maj. Gen. Roger Teague, director of space programs, told reporters that OCX “continues to see ups and downs,” but that overall, it “continues to stabilize.” The service has also pushed back the procurement of two GPS III satellites from FY18 to FY19, Annicelli said. The move was made in light of “longer life expectancy of the current GPS II on-orbit,” she said. The extra time will also allow the service to “to fully evaluate the follow-on acquisition strategy” for GPS III satellites 11 and after. The first GPS III satellite is expected to launch in 2018, with up to 32 satellites expected for the full constellation.