Axarajee,... you are right when you say the number of hours RA aircrafts flew during these 20 yrs should also be counted. But then, as far as RA's B-757s are concerned in this wide span of 20 yrs ( in my rough calculatio they might have logged 35000 to 40000 hrs ) the casualty ratio is still zero. In Asian standard ( please note that in my earlier posting I was comparing with Asian airlines), this is not bad if not good !