Dallas/Atlanta: US airlines tumbled the most among industry groups on the S&P 500 Index as concerns mounted that President Donald Trump’s ban on travel from seven predominantly Muslim nations will chill demand for flights.

Investors are fearful that US restrictions will expand or be answered with retaliation by other nations, said Joe DeNardi, an analyst at Stifel Financial Corp.

Airlines plunged 4.3% at 10:58 am in New York, almost quadrupling the 1.1% drop of the broader index.

“Should you see it spread or more stringent restrictions on travel into the US be enforced, that’s the concern," DeNardi said in an interview.

Trump’s 27 January order sparked a weekend of chaos and confusion at airports around the world, fueled by uncertainty over which passengers were barred. While none of the three biggest US airlines flies to any of the countries, their global alliance partners do. The ban covers people from Iraq, Iran, Syria, Yemen, Sudan, Somalia and Libya.

American Airlines Group Inc., the world’s largest airline, fell the most among peers, dropping as much as 6.6%. That was the biggest intraday decline in seven months.

Three US courts have temporarily blocked parts of Trump’s plan. Bloomberg