Here's what the Air Force says about the U-2s:
"The U-2R, first flown in 1967, is significantly larger and more capable than the original aircraft. A tactical reconnaissance version, the TR-1A, first flew in August 1981. Designed for standoff tactical reconnaissance in Europe, the TR-1A was structurally identical to the U-2R. The 17th Reconnaissance Wing, Royal Air Force Station Alconbury, England used operational TR-1As from 1983 until 1991. The last U-2 and TR-1 aircraft were delivered to the Air Force in October 1989. In 1992 all TR-1s and U-2s were designated U-2Rs. After re-engining with the F-118-101 engine, they were designated U-2S."