In the busy summer travel period in Cuba, a long line of people wait for hours in the sweltering heat outside the Havana office of state-owned airline Cubana, many of them eager to visit families in the provinces.

But they are not waiting to book flights. Instead, they hope to get their money back on plane tickets or exchange them for bus tickets across the island.

Cubana, which has a virtual monopoly on domestic flights in Cuba, said last month it was suspending nearly all of them due to a lack of working aircraft, plunging travel on the Caribbean's largest island into chaos.