I have seen the movie twice, once as a child and once as an adult. Both times it held up extremely well; this is a heart-wrenching story about life and death at the front.
The film follows the 'life' of a fighter/interceptor squadron; with newbies - still wet behind the ears - arriving and slowly becoming the 'old men'. The happenings are very true to life and feel completely believable; both compared to memoirs of Soviet Aces I have read, and testimonied by the intersplicing of real war footage into the film (which is why the whole film is black and white).
The dialogue is brilliant and many lines from the film have entered common Russian parlance; this is unfortunately lost on british audiences.
In summary, I highly recommend this movie to anyone who can get a half decent translation of it. (I watched the film in Russian)