Having just said how much I like QR , that made me think: if I go OSL-LHR-xDOH-SYD then US then LHR-OSL, is it allowed to do the US-UK bit back through DOH on QR? I think we are allowed to go through DOH twice because one is a direct flight to S Pacific, but would it violate the continuous TC1-2-3 rule?
Re the TC1-TC2-TC3 routing rule, from the User Guide:
The ticket rules divide up the world into three “Tariff Conferences” (TC) each having two continents; as follows:
TC1 = North and South America
TC2 = Europe/Middle East and Africa
TC3 = Asia and South West Pacific (SWP)
Notes:
Europe/Middle East includes the countries of North Africa (Morocco, Algeria, Tunisia, Libya, Egypt, Sudan)
Russia is split between Europe/Middle East and Asia (the split is at the Ural Mountains),
Main Routing Rules: You must visit all three Tariff Conferences – you will of course be starting in one of them, so you must visit the other two in order (travelling either eastbound or westbound), and complete your RTW journey by returning to your starting TC; generally you must return to your starting country (there are exceptions - see More Rule Details below for more information)
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So for your itinerary, you are starting in TC2 then heading East to TC3 followed by TC1 and finally back to TC2. On your TC1-TC2 crossing you can most certainly fly US-Doha and, if you cared to, follow this with Doha-Africa-Doha before finally returning to the country of origin to complete the RTW