As the previous posts outline, the mix of experience is quite legal. Before you can really answer the question of wether or not it is safe, you need to consider what exactly was it that brought you to notice the gap in experience. It could be that the crew were very new to that particular airline but may have been flying for many years, so as far as if anything should go wrong then you are in the hands of good people. Getting used to a new airline and its service may give the impression that you are new and inexperienced.
As a purser for an airline which has heomorraged experienced crew I can tell you that whilst it may be legal to operate to minimum crew (3 on the 733, before an a/c can come into service it has to be proven that it can be evacuated in less than 90 seconds using only half the exits, thats partly why levels are set as they are, 1 crew for 50 pax seats), it is far from ideal to have only one experienced person on board. Yes its right to say that all crew undertake very intensive training and would not be allowed out to fly unless they had passed rigorous tests, that is exactly what it is; TRAINING. It takes considerable time to become accustomed to the strange environment that you are working in. A very important part of that learning curve involves learning from those about you, how can you do that if there is no one else there to give it to you?
The legal minimum is fast becoming the industry standard which is not what it was set out to be; which is the closest you can legally operate without being unsafe. That does not only apply to crew levels but rest and maximum flying hours etc (how many of us can honestly say that we are on the ball at the end of some of the duties we do these days?). But companys have to stay financially viable, so it will take a tragedy that can be directly linked to those legal minimums being taken as standard to change things.
That is not to say that just because you are new you cannot still be damn good. (thought i'd better get that in!)
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