How to do it
The most economical way to circumnavigate is to buy a round-the-world air ticket that uses one airline alliance. Theoretically, any routing is possible, but knowing how the RTW booking system works will make your trip cheaper. For example, the Star Alliance, a coalition of 27 airlines, offers a RTW ticket with a maximum of 15 stops. Its member airlines fly to 1185 airports in 185 countries.
There are rules: you must follow one global direction (east or west – no backtracking); you must start and finish in the same country; and you must book all your flights before departure, though you can change them later (which may incur extra charges).
How long you need
You could whip round the world in a weekend if you flew non-stop. However, the minimum duration of most RTW tickets is ten days – still a breathless romp. Consider stock-piling annual leave, tagging on public holidays or even arranging a sabbatical in order to take off two months, ideally six to 12. The maximum duration of a RTW ticket is one year.
When to go
The weather will never be ideal in all your stops. So, focus on what you want to do most and research conditions there: if a Himalaya trek is your highlight, donʼt land in Nepal mid-monsoon; if you want to swim with whale sharks off Western Australia, be there April-July. Then accept youʼll be in some regions at the ʻwrongʼ time – though this might offer unexpected benefits (for example, Zambia in wet season means lush landscapes and cheaper prices).