Many airlines have suspended flights to and from Qatar's capital, Doha.
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.
Those countries have now closed their airspace to the country's flag carrier, Qatar Airways.
So what should passengers do?
Who is directly affected?
Anyone who'd planned flying direct between Qatar and the UAE, Saudi Arabia, Egypt, Bahrain will be impacted.
So too are passengers to/from those four countries who were due to be transiting through Qatar, for instance Singapore to Cairo via Doha or London to Riyadh via Doha.
I am booked on a Qatar Airways flight to/from UAE/Saudi Arabia/Bahrain/Egypt. What shall I do?
Qatar Airways has suspended all flights to those four countries until further notice.
Passengers with confirmed bookings with a travel date between 5 June and 6 July 2017, can get a full refund on any unused ticket.
You also have the option to rebook up to 30 days after your confirmed departure date. This will be free of charge, but you can only change once.
Passengers with existing bookings should call +974 4023 0072 or contact their nearest Qatar Airways office.
I am due to transit through Doha on Qatar Airways - en route to the UAE/Saudi Arabia/Bahrain/Egypt. What about me?
It won't be possible. But under the rules of airline industry body IATA, you must be offered the option of being rebooked onto other carriers.
So if, for example, you are due to fly from London to Dubai, via Doha, Qatar Airways has to find you an alternative - either a direct or indirect flight.
It says it will do that, but it all depends on availability, so potentially you may not travel exactly when planned.
Again, to make these arrangements call +974 4023 0072 or contact your nearest Qatar Airways office.
I am booked to fly on Qatar Airways to other destinations. What has changed?
The airline says things proceed as normal. You can still fly in and out of Qatar's hub in Doha.
So a journey from, say, Singapore to London via Doha is unaffected.
But because Qatar Airways is not using the airspace of Saudi Arabia, the UAE, Bahrain or Egypt it has just a narrow strip to operate in, meaning it is having to take different routes.
On some routes this will add to flight times (as well as Qatar's fuel bill) - though the airline has not yet said how much difference it is likely to make to trip durations.
Which other airlines are affected?
It's not just Qatar Airways. If you are due to fly in or out of Qatar from the UAE, Saudi Arabia, Egypt or Bahrain then your flight will not be taking off.
Airlines operating these routes include Etihad, Emirates, Flydubai, Air Arabia, Gulf Air, Saudi Arabian Airlines (Saudia) and Egyptair.
All airlines seem to be offering the same options - either a full refund on unused tickets or rebooking onto the nearest alternative destination on its network.
Etihad: Passengers should call +971 2599 0000 or visit its website.
FlyDubai: Call +971 600544445, +974 4 4227350/51, contact your travel agent or send a private message to its Facebook page.
Air Arabia: The airline - which operates from two of the UAE's northern emirates - says passengers should call +971 6 5580000 or go to its website.
Gulf Air: Passengers booked on Bahrain's national carrier can call +973 17373737 or visit its website.
Saudia and Egyptair have not issued specific contact numbers.
I want to get between Qatar and UAE/Saudi Arabia/Bahrain/Egypt. What are my options?
Given there's no direct travel, you could fly to another location that is not part of the ban, and then go from there.
For example Oman Air and Kuwait Airways are still operating Doha flights so passengers could travel via Muscat or Kuwait City.
Bear in mind though that if you are a citizen of the UAE, Saudi, Bahrain, Egypt, Yemen or Libya you won't be allowed into Qatar, and vice versa, Qataris are being told to leave countries that have cut ties.
How long will these restrictions go on for?
There's no fixed end date for this.
Nobody appears to be taking any booking on this route for the next month. Of course there's a chance this will be resolved sooner than this. Or, indeed, that it will go on far longer.