Is Visa needed for military for 48 hr lay over in China

my daughter is traveling to China with her boyfriend that is in the Army and stationed in Korea, they are stopping in China for 2 days on his way back to Korea, she will be turning around to return home. Do they both need Visa's? They have stand by tickets because my daughter works for American Airlines. They will be in the airport waiting for their flights before the 48 hour time limit but not on the plane for an hour later.