Are you better off flying with a trainee pilot, or being operated on by a trainee surgeon?

One of the concerns that some people have relates to the way we train our doctors, essentially an apprenticeship system, with a trainee learning from a senior doctor. While I have some concerns about other aspects of this system, one of the unavoidable consequences is that trainees have to practice upon a patient. Is this safe? Surely being operated on by someone with less expertise increases the risk of something going wrong?
A study has just been published seeking to answer that question. The American College of Surgeons examined patient outcomes in more than 600,000 operations. They found that having a resident, (junior surgeon in training) while associated with a slightly higher risk of developing (usually minor) complications, was also more likely to be associated with a slightly reduced risk of death. The reasons obviously are unclear, but this important paper does provide some reassurance.