Corrected entry: Jamie is captured and put in a prison camp in early 1942, yet he has no problem recognizing and knowing the name of the P-51 Mustang plane, which was only even introduced into USAF later that year, and didn't arrive in China until 1943-44.
Corrected entry: Jim doesn't age during the movie. He was in the prison camp for about three and a half years. When we first see him he looks about 12. By the end of the movie he should be a gangly teenager but he hasn't aged a day.