Malakal is a city in South Sudan.
The airport serving the city is Malakal Airport (IATA: MAK), it's South Sudan second international airport with flights from Addis Ababa by Ethiopian Airlines  and from Khartoum with Sudan Airways . There is also a domestic route with Juba. Notice that the plane from Juba is often booked full; make early reservations.
The main mean of transportation is along the White Nile with barges traversing up and down. There are boats from Maloot taking passangers, travel time varies widly with a journey taking anything from six to 24 hours.
It is relatively cheap and easy to secure passage on a motorboat from Juba. However this will involve around 6 days and nights of very remote and uncomfortable travel and it is highly advisable to bring a mosquito net, something to sleep on, bottled water, food and medical supplies.
The roads in South Sudan range from bad to non-existent; and during the rainy season, all roads to Malakal become unusable for ordinary vehicles. However, they are slowly being repaired, especially the one towards the Ethiopian border.