British Airways (BA) is the flag carrier airline of the United Kingdom, headquartered at Waterside, Harmondsworth, near its main hub at London Heathrow Airport. It is the second largest airline in the United Kingdom, based on fleet size and passengers carried, behind easyJet. In January 2011 BA merged with Iberia, creating the International Airlines Group (IAG), a holding company registered in Madrid, Spain. IAG is the world's third-largest airline group in terms of annual revenue and the second-largest in Europe. It is listed on the London Stock Exchange and in the FTSE 100 Index. British Airways is the first passenger airline to have generated more than $1 billion on a single air route in a year (from 1 April 2017, to 31 March 2018, on the New York JFK - London Heathrow route).