Air travel across the Gulf region and beyond faces major disruption following the move by Saudi Arabia, Egypt, the United Arab Emirates (UAE) and Bahrain to sever ties with Qatar, accusing the tiny oil rich state of supporting terrorism.
Saudi Arabia on Monday banned Qatari airlines from its airspace, while Abu Dhabi's state-owned Etihad Airways and Dubai's Emirates Airline said they would suspend all flights to and from Doha from Tuesday morning until further notice.
Qatar is home to global airline Qatar Airways and many airports in the Gulf region are major hubs for international connecting flights. Qatar's main Hamad International Airport, for example, served around 9.8 million passengers in January-March, according to its website.
"There is a wider impact than Qatar Airways not being able to land in markets like Saudi and UAE since those markets are significant sources for transfer traffic," said Will Horton, a senior analyst at CAPA Centre for Aviation in Melbourne.
"A Riyadh passenger may not be able to connect to Bangkok via Doha and a Dubai passenger could not get to London via Doha."
The harshest restrictions came from Saudi Arabia's General Authority of Civil Aviation (GACA), which banned all Qatari planes from landing at the kingdom's airports and stopped them from crossing Saudi airspace. It also banned Saudi commercial and private air operators from serving Qatar.
Bahrain's civil aviation authority, meanwhile, announced flights to and from Qatar had been suspended, according to state news agency BNA.
Among airlines, flydubai and Bahrain's Gulf Air joined Etihad and Emirates in saying they would suspend all flights to and from Doha. Qatar Airways said on its official website it had suspended all flights to Saudi Arabia.
Saj Ahmed, the UK-based chief analyst at StrategicAero Research, warned of disruptions in the Gulf Cooperation Council (GCC) states of Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the UAE, as well as further afield.
"Airspace will be impacted by flights being re-routed, especially for Qatar Airways who will no longer be allowed to use the expansive airspace of Saudi Arabia on flights to Europe and North America," he said.
"Equally, the litany of narrowbody jets that Qatar Airways has to park which can't be used for intra-GCC flights will hit operations at Doha since ramp space will be at a premium - this could lead to flight delays and incur more costs."
Qatar Airways does not break down revenue figures for the Gulf region. Last year, its parent company published financial results for the first time. These showed a net profit of 1.6 billion riyals ($439 million) for the year to March 31, 2016, up from the 374 million riyals in the previous year.
The row between Gulf states is a fresh challenge for the region's airlines at a time when U.S. President Donald Trump is trying to restrict the travel of passengers to the United States from some Muslim-majority countries.
U.S. authorities have also banned the use of most electronic devices on board aircraft from some Middle Eastern origins.
The restrictions on Qatar are more severe than during a previous eight-month rift in 2014, when Saudi Arabia, Bahrain and the UAE withdrew their ambassadors from Doha, again alleging Qatari support for militant groups. At that time, travel links were maintained.