Originally Posted by
anabolism
A side trip is just a set of one or more flights that are priced and ticketed separately from the RTW. They can be in the same PNR if you make the booking using a travel agent, or an airline willing to do it. The agent puts all your desired flights in the record, then prices and issues the 16 segments of the RTW, then prices and issues the other segment(s).
That’s not quite correct. A side trip is a journey which interrupts the travel under a fare component, but is still on the same ticket. The side trip is calculated separately under its own fare(s) as appropriate as you say. But, in every other respect, it’s part of the journey and counts towards the sixteen sector limit. The side trip will be printed in brackets (parentheses) in the horizontal calculation box on the ticket. A connection to/from a side trip is the same as any other kind of connection in terms of taxes or missed connection protection. Unless the airline staff read the fare calculation box, it won’t be obvious that you are making a side trip.
Attached is an example from the Ticketing Manual.
Side trips are typically not auto priceable.
Separate tickets are not governed by the fare rules. No one can stop you buying a separate ticket.