Many of Sudan's land borders are closed or unsafe, but travelers can arrive overland from Egypt, or via ferry from Egypt or Saudi Arabia. Visas should be requested well in advance, as there are sometimes difficulties obtaining them at the border. Within the country, Sudan Airways flies to most large towns, and luxury buses drive regularly to the major Northern cities. Trucks and makeshift buses provide access to other areas where roads may not be maintained, as infrastructure is highly undeveloped outside Khartoum