By Alexandra Alper MEXICO CITY (Reuters) – Mexico is reviewing design plans for a new 120 billion peso ($9.23 billion) Mexico City airport which will eventually have six runways and should begin operating by 2018, according to sources familiar with the plan. The new hub is due to replace the overstretched Benito Juarez International Airport and would be built on the area of the Texcoco lake bed nearby, said two people with knowledge of the project, few details about which have been revealed. The current airport, Latin America’s second busiest after Sao Paulo’s Guarulhos, exceeded maximum operating capacity more than 50 times in 2012, and a new one has been discussed for years. “This situation implies a loss of competitiveness to foreign airports and on some occasions, security risks,” President Enrique Pena Nieto’s transport development plan says.