While engine failures in all phases of flight are not very common among aircraft today, they were a fairly frequent occurrence, according to SKYbrary, an electronic aviation safety knowledge repository. The source also noted that statistics from the 1960s indicate that failures resulting in inflight shutdowns occurred at an approximate rate of 40 per 100,000 flight hours, equivalent to 1 per 2,500 flight hours, or every engine failing once per year. Today, the failure rate of the engines installed on current-generation aircraft is reportedly less than 1 per 100,000 flight hours.