He's a local boy who was only less than a mile from the airport when he ran off whilst shopping with his mum. You do see a lot of local children watching planes land, both inside and at the perimeter of the runway fencing. The airport is right next to a massive housing estate, where he lives - a matter of yards away at some points. Locals do go in the airport for drinks and meals, including fast food, as it's nicer than local facilities around the estate. I wouldn't be surprsed if he's familiar with quite a few areas around the airport.