Major global airlines including British Airlines, Emirates and Air France began boarding passengers bound for the United States after a court order lifted a travel ban imposed on them a week earlier by US President Donald Trump.

A Seattle-based federal judge, James Robart, on Friday issued a nationwide order blocking Trump's ban on nationals from seven Muslim-majority countries, in the most severe legal blow to the president's executive order.

Trump has slammed the decision as “ridiculous” and vowed it will be overturned.

Although a few airlines said they were waiting to see how the situation developed, carriers including Air France, British Airways, Emirates, Etihad Airways, Lufthansa, Qatar Airways, Swiss Airways and United Airlines said they would allow nationals of the countries in question to board if they had a valid visa.

“Since this morning we have applied with immediate effect the (US) judicial decision taken overnight. All passengers presenting themselves will embark once their papers are in order to travel to the United States”, an Air France spokesman told AFP.

Swiss airline said it was in touch with US customs and border services and that “at the present time all passengers with valid travel documents can travel on any Swiss flights bound for the United States.”

Germany's Lufthansa also cited the court injunction and underscored that those “holding a valid immigrant or non-immigrant visa for the US are again allowed to travel to the USA”.

Trump's January 27 executive order placed a 90-day ban on nationals of Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen from entering the United States and blocked for at least 120 days the arrival of refugees. Syrian refugees were banned indefinitely.

The State Department said up to 60,000 people from the seven Muslim-majority countries had had their visas cancelled. A Justice Department attorney put that figure at closer to 100,000.

Hours after the federal judge's decision, the State Department told AFP that it had “reversed the provisional revocation of visas” and that visa holders from the targeted countries were again allowed to travel as long as their documents had not been “physically cancelled”.

The Department of Homeland Security - which runs border agencies - also said it would cease implementing the order.

Fly while you can

Trump's move, which he justified on security grounds, wrought havoc at airports across America, sparked protests and left countless people hoping to reach the United States in limbo.

The US leader lashed out on Twitter hours after the court ruling, calling the federal judge Robert a “so-called judge” and denouncing his decision as “ridiculous”.

“When a country is no longer able to say who can, and who cannot, come in & out, especially for reasons of safety & security - big trouble!” Trump tweeted.

He added that “certain Middle-Eastern countries agree with the ban. They know if certain people are allowed in it's death & destruction! In Tehran, one travel agent advised Iranians wishing to fly to the United States to “take a plane to any city this evening,” warning the repeal of the ban may not stand.

Some carriers, including low-cost carrier Norwegian, said they were waiting for official confirmation and advised passengers to contact US authorities for more information.