A U.S. F-16 fighter appears to have crashed into Yellow Sea waters off the coast of South Korea, stoking safety concerns after eight U.S. airmen were killed last month in the crash of an Osprey aircraft near a Japanese island. The F-16 crashed into the sea Monday after taking off at about 9 a.m. from Gunsan, some 180 kilometers (110 miles) south of Seoul, Yonhap News Agency reported, citing…