Qataris will no longer be allowed to land at any airports in the United Arab Emirates or catch connecting flights there as part of increased efforts by Arab powers to isolate the Gulf state.
The UAE's state-owned Etihad Airways, meanwhile, said all travellers holding Qatari passports were now prohibited from travelling to or transiting through the emirates on government instructions.
"This ruling applies to all airlines flying into the UAE, including Etihad Airways", the Abu Dhabi-based airline said.
The United Arab Emirates had already said Qatari nationals would not be allowed to enter the country or cross its points of entry, although the practical effects on airline passengers had been unclear until now. "I have no choice because it can not fly anymore".
While applauding a Kuwaiti effort to mediate the crisis, Gargash said Emirati and Saudi officials planned to concede nothing to Qatar, an worldwide air travel hub now cut off from some of the skies around it and blocked from receiving the trucks full of food it relies on to feed its citizens.
Qatar Airways has cancelled all flights to those countries, which averaged 55 a day before the diplomatic row, according to CAPA Centre for Aviation.
Tourism Minister Arief Yahya expects Indonesia to lose thousands of Middle Eastern tourists due to boycott of Qatar Airways.
Qatari nationals will now not be allowed to pass through airports in the UAE even to change planes. A Maersk Line spokesman said: "We have confirmation that we will not be able to move Qatar cargo in and out of Jebel Ali".
UAE Minister of State for Foreign Affairs Anwar Gargash told Reuters there would be more economic curbs on Qatar if necessary and said Doha needed to make ironclad commitments to change what critics say is a policy on funding Islamist militants.
The Pentagon was unable to reconcile Trump's support for Qatar's isolation with its own praise for the country.
"The Qataris should not count on that base as being a guarantee of sort of American protection when it comes to conflict with Saudi Arabia", Al Qassemi said. An Islamic Religious Council of Singapore spokesman said alternative flights to Saudi Arabia were being sought, with less than 200 people affected.
A spokesperson for SNC-Lavalin, which last year got a five-year engineering consultancy and support services contract for a gas-to-liquids complex in Qatar's Ras Laffan Industrial City north of Doha, said the company is "closely monitoring the situation and is in communication with local managers".