NATO helicopters on Tuesday once again violated Pakistani airspace in the FATA region, reported a private TV channel. The helicopters flew up to 600 metres inside Pakistan, over the areas of Borki, Kharlaki and Kurram and remained in Pakistani airspace for 20 minutes. NATO helicopters had earlier twice violated the airspace, including the one which led to the killing of three Pakistani security personnel. Pakistan had closed the border with Afghanistan after the incident, halting NATO supplies going through the country.