Connecting Flights

I just wonder for realistic worlds how an airline would have a connecting flight ( i.e. Manila-Los Angeles-Sao Paolo non-stop by a Philippine airline) or another example ( Miami-Singapore-Jakarta by an American airline) or having fifth freedom like (Amsterdam-Bangkok-Sydney by a Dutch Airline with Bangkok serves as stopover for Sydney flights and has no direct service from Bangkok to Sydney)? I just want to serve all continents (excluding Antarctica).