Airline stocks plunged more than 4 percent Monday in the first trading since President Trump’s executive order temporarily barring citizens of seven majority-Muslim countries from entering the United States.

Stocks in commercial airline companies fell 4.3 percent Monday morning, according to Bloomberg, more than four times the 1.1 percent opening drop on the S&P 500 index.

Border control agents have detained legal permanent residents, visa holders and refugees from the affected countries entering United States airports this weekend.

The sudden, confusing implementation of the ban starting late Friday roiled airports around the country, with protests erupting and lawyers rushing to help travelers affected.

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Stock in American Airlines Group fell the most Monday, falling 6.3 percent as of 11:55 a.m. Shares of United Airlines’ holding company fell 4.8 percent in the same time frame, while shares of Delta and JetBlue’s parent companies fell 3.9 and 2.6 percent, respectively

Trump on Friday signed an executive order banning Syrian refugees indefinitely and halting the all refugee resettlement for four months. The order also blocks entrance to the U.S. for 90 days for people from seven predominantly Muslim countries: Iran, Iraq, Yemen, Somalia, Syria, Sudan and Libya.

Three federal courts have temporarily blocked parts of Trump’s order, and Homeland Security Secretary John Kelly said Sunday that U.S. legal permanent residents from those countries should be allowed back into the country.