art museum detroit Round-the-world tickets are offered by airline alliances, a sort of partnership among groups of airline carriers. The three biggest alliances are Oneworld, Sky Team and Star Alliance. The alliance agreement makes booking round-the-world passes easier and usually cost-effective. Purchasing a round-the-world ticket from an alliance group also lets you collect mileage points inside same group, providing a good accumulation of points once you return home (to be used on the next trip!).