It's long been a bit of an oddity: according to the rules, Qantas Platinum and Platinum One-grade frequent flyers have been able to bring a guest into the airline's first class lounges at Sydney, Melbourne and Los Angeles only if that guest was travelling on the same flight as their host.
However, according to Oneworld alliance, to which Qantas belongs, any Oneworld Emerald member – the equivalent to Qantas Platinum – can bring a guest into any first class lounge as long as that guest is travelling on any flight "operated and marketed by a Oneworld carrier."
Staff at the Qantas First Lounges have generally been very flexible in following the more generous Oneworld interpretation rather than the airline's own.
However, it's worth noting that Qantas has now officially changed its own lounge access rules to clarify that position and formally follow Oneworld's lead when it comes to who you can bring into the first class lounge as a guest.
So, if you're a Platinum-grade Qantas Frequent Flyer heading back to Sydney from Los Angeles while a less status-blessed colleague in business class is headed to Hong Kong on a Cathay Pacific flight, you can now both make a beeline for the Qantas First Lounge at LAX.
Two caveats remain in the amended Qantas lounge access rules: if you're flying on Jetstar or Emirates, then your guest must also be travelling on that same flight. This reflects the fact that neither of those airlines is a Oneworld alliance member.