The Energy Atlantic, a 290-metre tanker steaming slowly through the Gulf of Mexico, is about to make history. It is scheduled to arrive on Tuesday at Cheniere Energy’s Sabine Pass liquefied natural gas plant on the coast of Louisiana, to be loaded with the first cargo of LNG to be exported from the “lower 48” contiguous states of the US. The shipment is a momentous event for energy markets, marking the arrival of the US as a gas supplier to the world. The plunge in oil prices since the summer of 2014 has dragged down the value of LNG, which is often sold on crude-linked contracts, and damped the excitement over US exports. The economics of shipping gas from the US were compelling two years ago, but are now marginal. Deteriorating market conditions have put the brake on any new investments in US LNG. Even so, US LNG exports are likely to have a significant impact, holding down energy costs for consumers in Europe, Latin America and Asia. They will also provide tough competition for anyone hoping to build rival LNG plants, such as the proposed projects in east Africa, the west of Canada, or Russia. By the end of the decade, the US is likely to be the world’s third-largest exporter of LNG, after Qatar and Australia.