The company traveling between Fortaleza and Natal is Viação Nordeste. Its site contains schedules and prices. The trip lasts 5 hours and costs from R$69 (basic bus, with no air con).
Careful. There were several hold-ups during the year 2008. The armed robberies on buses travelling between the two cities took place in the western part of the state of Rio Grande do Norte. We do not advice night travel on that route – all the hold-ups happened at night time.