During John Glenn's first orbital flight, an indicator went off, causing concern over the heat shield. Kraft and his team correctly determined the heat shield

During John Glenn's first orbital flight, an indicator went off, causing concern over the heat shield. Kraft and his team correctly determined the heat shield was fine. His judgement was ignored and he was forced to use an untested and unnecessarily risky procedure. Decades later, both Glenn and Kraft went on the record denouncing what happened. As a result, Kraft would define NASA policy as "the flight director may, after analysis of the flight, choose to take any necessary action required for the successful completion of the mission." I can't imagine how Apollo 13 would have unfolded if this policy was not in place.