Haul out your frequent flyer card from your wallet. Now take a good look at it. Can you spy a small logo which says Oneworld, Star Alliance or SkyTeam?
If so, that card could unlock plenty of prized travel perks of which you may be completely unawares.
The holy trinity
Oneworld, Star Alliance and SkyTeam are three airline alliances: over-arching 'families' of airlines, intended to make life much easier for the business traveller.
A central plank of this is extending to the frequent flyers of one airline an equivalent set of benefits with airlines in the same alliance.
Qantas is a founding member of the Oneworld group, and when flying on any Oneworld airline – even in economy – Gold members of the Qantas Frequent Flyer program can use that airline's business class check-in desks and business class airport lounges.
A world of perks
Oneworld's extensive membership roster includes American Airlines, British Airways, Cathay Pacific, Finnair, Japan Airlines, Malaysian Airlines and Qatar Airways.
Platinum-grade Qantas flyers enjoy a higher level of perks such as access to first class lounges regardless of their class of travel.
(Note that Emirates isn't part of Oneworld, but the Qantas-Emirates alliance affords similar rights to card-carrying Qantas frequent flyers.)
When flying on those and other Oneworld airlines a flash of your card also provides other useful benefits such as a higher checked luggage allowance.
The more you know
I mention all this because last month on a trip to Hong Kong I bumped into a fellow traveller who, despite holding top-tier Platinum One status with Qantas, had no idea that he could use Cathay's superb The Pier First Class lounge at Hong Kong airport – even though he was flying with Qantas.
This chap was oblivious to the perks of being a high-grade frequent flyer in any Oneworld airline.
Your pick of lounges
Where there are several lounges operated by Oneworld airlines you can choose which one you'd like to use, and even visit more than one if you wish.
In the case of terminal three at London's Heathrow Airport, an increasing number of British Airways and Qantas travellers are skipping the down-at-heel BA lounge for the newer and far superior Cathay Pacific first class and business class lounges.
At terminal one of Singapore's Changi Airport, Qantas and British Airways flyers can sample lounges run by both airlines (my vote goes to the Qantas lounge).
Star Alliance, which this month celebrates its 20th anniversary, is Oneworld's main competitor.
While Star Alliance has no local airline under its wing – despite the constant wishes of many frequent flyers that Virgin Australia would sign up – Star has 11 member airlines flying in Aussie skies.
This includes Air New Zealand, Singapore Airlines, United Airlines, Air Canada, ANA and Thai Airways. Lufthansa, Swiss, Austrian Airlines and SAS are also popular choices for Aussies flying to Europe via Singapore and Hong Kong.
Rounding out the troika is SkyTeam which counts airlines such as China Southern, Korean Air, Vietnam Airlines, Air France and US carrier Delta in its corner.
In each case, top-tier membership in the frequent flyer scheme of one member airline comes with valuable privileges across the rest of the family.
That said, lounge access across alliances can still come with a few wrinkles.
The fine print
Gold-grade Star Alliance members don't get entry into Singapore Airlines' flagship business class lounge at Changi terminal 3 – instead they're shunted into a woeful KrisFlyer Gold lounge.
Oneworld's more consistent lounge access policy is a win for business travellers, but there are still airlines such as British Airways and Qatar Airways which reserve their best home airport lounges for their own first class flyers, regardless of the colour of your shiny frequent flyer card.
You can also earn frequent flyer points and status credits for the airline of your choice when travelling on another airline in the same alliance.
The rates are not always as generous as you'd wish: for example, you stand to earn substantially fewer Qantas points and status credits flying on a Oneworld partner than with the Red Roo itself over the same route.
The DIY airline
But is it better to earn fewer points than none at all? Absolutely.
Rather than join one of the established alliances Virgin Australia has adopted a DIY approach, forging partnerships with Air New Zealand, Singapore Airlines, Etihad and Delta on 'best fit' principles to build out Virgin's international network.
Few people spend more time on planes, in lounges or mulling over the best ways to use frequent flyer points than David Flynn, the editor of . His unparalleled knowledge of all aspects of business travel connects strongly with the interests of 51698009 readers.
How significantly do airline alliances shape your travel plans, and which alliance do you rate as the best – or do you find that alliances are becoming less relevant to your needs?