A “substantial underperformance” in travel to the US is being reported following president Donald Trump’s travel ban on certain mainly Muslin countries.

The claim comes from ForwardKeys, which predicts future travel patterns by analysing more than 17 million flight booking transactions a day, as the US Supreme Court starting hearing arguments about the legality of Trump’s order.

Latest reports suggested the court was leaning in favour of a third version of the travel restrictions, covering Iran, Libya, Somalia, Syria and Yemen as well as North Korea.

Federal judges in Hawaii, California, Maryland and Virginia have rejected different versions of the executive order as unconstitutional in the 15 months since Trump handed down his first travel ban.

The appeals process ultimately placed the fate of the travel ban with the highest court in US, wit a ruling not expected until June.

ForwardKeys chief executive Olivier Jager said: “In the period between Donald Trump announcing his first travel ban and the federal judge’s initial temporary blockage, bookings for inbound travel to the USA fell 6.5%, a phenomenon which has since been named the Trump Slump.

“In the 15-month period between that first announcement and now, inbound travel to the USA was 1.4% down while global international travel grew 5% on the equivalent period a year earlier.

“Looking ahead for the coming three months, flight bookings to the USA are 2.9% ahead of the equivalent period the year before.

“However, flight bookings globally over the same period are 5.9% ahead, so one has to conclude that since announcing the first travel ban, the USA has underperformed in the context of robust global travel demand.”

Jager added: “ForwardKeys is not claiming that the United States’ inbound travel difficulties are caused by Donald Trump’s policies – not least because exchange rates have been challenging.

“For example, in the period January 2017 – March 2018, the value of the pound and the euro appreciated 13% and 16%, respectively, against the dollar, making the US a significantly more expensive destination.”