Continuity mistake: Right before Ben jumps off the cliff, he drinks a small cup of coffee and places it back on a saucer that Jonathan is holding. When the shot cuts, the saucer is still visible in Jonathan's hand, but the cup cannot be seen on it. The cup then reappears in the next shot.
Answer: In the book of the same name, this man is called "Pig". He was a test pilot during the Vietnam War. He played a crucial role in training the new pilots.