The online community provides expert recommendations on the best restaurants bars, shops, neighbourhoods and other places in both cities.
In addition, it helps users navigate the vast amount of internet information about the two cities and find the best content quickly.
It enables members to review, rate, save, create profiles, suggest ‘twins', follow other members' recommendations and make their own maps and lists.
The network also provides Amazon.com-style personalised recommendations based on user behaviour, and gives every place a score out of 100, which changes dynamically, based on user behaviour.
Chris Davies, the digital marketing manager at British Airways, said: "British Airways is a company which connects people and social media is about connecting people.
"We fly more people between London and New York than anyone else. Creating a community website about the best of what's on offer in the two cities we know best is a credible and useful tool."
The project was jointly created by three agencies: BBH oversaw the commercial and strategic side, Made By Many created the design of the network and Agency.com handled development and delivery.
BA is also planning to launch mobile phone applications linked to the network at an unspecified date.