(LEAD) S. Korea's trainer jet conducts 1st test flight in U.S.

(ATTN: CLARIFIES about the project name of T-X in 3rd para; CHANGES photo caption)By Choi Kyong-ae

SEOUL, Nov. 24 (Yonhap) -- South Korea's trainer jet made its first test flight in the United States last week after the two countries agreed to mutua