The US has banned toner and ink cartridges from passenger aircraft in the wake of last month's bomb plot. In addition, cargo flights from Somalia and Yemen are banned, Homeland Security Secretary Janet Napolitano said. High risk cargo will receive extra screening and parcels must be screened and certified to have come via an established shipper, she said. The strictures come after bombs hidden in cartridges were intercepted on route from Yemen to the US in cargo planes. The printer cartridge ban affects cartridges over 16 ounces.