Global airlines  have slashed a key industry profit by 21 percent amid concerns over an expanding trade war and higher oil prices.

The International Air Transport Association, which represents more than 80 per cent of global air traffic, said the industry is expected to post a $40 billion profit in 2019, down from the predicted December forecast.

The Association Director General Alexandre de Juniac said the airlines will still turn a profit this year, but there is no easy money to be made.