Travellers have reacted with dismay after many airlines suspended flights to and from Qatar's capital, Doha.
Some had to spend thousands of dollars on new plane tickets, while others are feared to be stranded at Doha's Hamad International Airport.
The issues arose after the United Arab Emirates (UAE), Saudi Arabia, Egypt, Bahrain, Libya and Yemen all cut diplomatic ties with Qatar.
They say it backs Islamist terror groups, which Qatar denies.
The Gulf allies have closed their airspace to Qatar Airways, which has suspended all its flights to Saudi Arabia.
UAE-based carriers Emirates, Etihad Airways, Flydubai and Air Arabia have said they will not fly to or from Doha from 6 June.
Bahrain's Gulf Air and Egyptair are expected to follow their lead.
Travel panic and a groceries rush
Robin Doodson, 43, who has lived in Qatar for three years, told the BBC he was due to fly to Australia via Abu Dhabi [capital of the UAE] on Thursday.
"It's a little bit chaotic - nobody knows what's going on here at the moment. Everyone's getting a bit panicky.
"Like everything here, there's no warning. You learn to expect the unexpected!"
Mr Doodson has booked a different flight to Oman, and says it will now take him two days to get to Australia.
As well as ceasing air contact, Saudi Arabia has closed its land borders with the tiny peninsula of Qatar. The move has prompted panic-buying in supermarkets, as about 40% of the desert nation's food is believed to be imported via the Saudi border.
The problem may be exacerbated by the Muslim holy month of Ramadan, currently under way, when participants fast during daylight hours and eat only after nightfall.
Supermarket sales tend to spike as local outlets slash prices and offer special promotions.
Mr Doodson said friends have sent him pictures of empty supermarket shelves, while hurrying to stock up on meat and other staples.
The local Doha News website told a similar story: "Customers could be seen piling their carts high with supplies of milk, water, rice and eggs at several popular grocery stores today, which were even busier than is usual for Ramadan."
The outlet quoted a shopper at Carrefour in Villaggio Mall, Doha, saying: "I've never seen anything like it - people have trolleys full of food and water."
A statement from Qatar's government said that "marine and air spaces will remain open for import and movement", and urged shoppers not to worry.
It added that food in Qatar is sourced from around the world, not just the Gulf.
Spending thousands on new tickets
Ron Moonsinghe, who works as a teacher in the UAE, told the BBC he and his wife had booked flights home to the UK via Doha, with Qatar Airways. Now he fears they will be cancelled.
"Those tickets cost us back in January 6,300 AED (£1,327; $1,715) for us both. I have just booked tickets with Etihad to London for 11,300 AED and have no idea how we can get a refund from Qatar Airways."
"This is bog-standard, cheapest economy tickets," he noted.
"This is going to affect hundreds and hundreds and hundreds of people - maybe thousands."
Mr Moonsinghe says the start of the school holidays on 22 June will exacerbate the problem. "There's hundreds of teachers going to different parts of the world... There's teachers here going to Australia, South Africa. Thousands of kids going all over the world - not just to the UK - and booked with Qatar Airways."
Lab scientist Richard Milkins, who is based in Saudi Arabia, was equally unimpressed.
He told the BBC: "This is a massive headache for a lot of people. In two weeks' time we have Eid Holidays in the Middle East. There will be many of us who have flights booked from Saudi Arabia and Bahrain via Doha to Heathrow, Manchester, Birmingham and Edinburgh.
"I have contacted Qatar Airways this morning with regards to my June 22nd flight Dammam-Doha-Birmingham, with the return leg June 30th, and have not received a response. Not Happy!"
There is also concern about the impact that closing the borders between Qatar and other Gulf countries could have on families.
Saudi Arabia, the UAE and Bahrain have given all Qatari visitors and residents just two weeks to leave their territory. The three countries have also banned their citizens from travelling to Qatar.
The Saudi authorities say an estimated 18,000 Saudis are living in Qatar, mainly as a result of intermarriage.
Some shared their concerns on social media, with one user noting, "Nobody deserves to be separated from their family".
What have the airlines said?
As of 5 June, Qatar Airways said it had suspended all flights to Saudi Arabia until 02:59 (Doha time) on 6 June.
According to Gulf News, representatives at Qatar Airways' call centre said passengers with bookings to and from the UAE "could assume their flights are on schedule".
"It is unclear how Qatar Airways plans to operate these flights considering that the UAE government has officially banned all Qatari means of transportation from coming to or leaving the UAE," the website noted.
In a statement online, Etihad said its last flight from Abu Dhabi to Doha would leave at 02:45 local time on 6 June, and the last flight from Doha to Abu Dhabi will be at 04:00.
The carrier said all customers with flights booked to and from Doha would be given "alternative options including full refunds on unused tickets and free rebooking to the nearest alternate Etihad Airways destinations".
Emirates said it would suspend flights to and from Doha from the morning of 6 June. It also said customers would be offered full refunds and free rebooking.
Dubai-based budget carrier Flydubai has urged passengers to contact their travel agent or its call centre to arrange a refund.