A possible trade war involving the US could hit demand for air travel, IATA has warned.

Announcing global figures for January, the aviation body said there has already been a slower start to the year, with traffic growth showing the slowest year-over-year increase in nearly four years,

But it said the figures were affected by the later timing of the Lunar New Year in 2018 as well as less favourable comparisons with the strong rise in traffic seen in late 2016 to early 2017.

“Despite the slower start, economic momentum is supporting rising passenger demand in 2018,” said Alexandre de Juniac, director general and CEO.

“That said, concerns over a possible trade war involving the US could have a serious dampening effect on global market confidence, spilling over into demand for air travel.”

January traffic rose 4.6% compared to January 2017, while capacity (available seat kilometers) rose 5.3% and load factor slipped half a percentage point to 79.6%.

European carriers’ international traffic climbed 6% in January compared to the year-ago period.

North American airlines saw a 3.5% rise in traffic over a year ago, but capacity rose 4.3% and load factor dipped 0.7 percentage point compared to a year ago to 79.6%.

Middle East carriers had the weakest growth, with demand up just 0.5%, the slowest pace since September 2008.

The Middle East market to and from North America was hit by the temporary ban on large portable electronic devices and Trump’s travel bans.