Swiss International Airlines has decided to abandon the "two in the cockpit at all times whilst flying" rule, according to articles
here and
here, as of 1 May 2017. (FlightAware and The Local CH.)
'A safety review “concluded that the requirement of having two crew members in the cockpit at all times during a flight does not enhance safety, and actually introduces additional risks to daily operations in flight safety terms (such as the fact that the rule results in more and longer openings of the cockpit door),” it said.' As well, SWISS complies with EASA rules regarding flight crew.