Following the April 1974 revolution in Portugal, the PAIGC became an active political movement in Cape Verde. In December 1974, the PAIGC and Portugal signed an agreement providing for a transitional government composed of Portuguese and Cape Verdeans. On 30 June 1975, Cape Verdeans elected a National Assembly which received the instruments of independence from Portugal on 5 July 1975. In the late 1970s and 1980s, most African countries prohibited South African Airways from overflights but Cape Verde allowed them and became a centre of activity for the airline's flights to Europe and the United States.