The diplomatic rift has wreaked havoc with airlines in the region, with major long-haul carriers such as Doha-based Qatar Airways and Dubai's Emirates suspending flights, leaving many passengers stranded at airports in the Gulf.
Several people have expressed concern on social media over disrupted travel, with images posted of travellers stranded at airports.
Twitter user @FahadBuwazir posted a photograph which he said showed Qatari citizens stuck at Jeddah's King Abdulaziz International Airport.
How travel will be immediately affected?
Qatar Airways, on its website, said it has stopped flights to Saudi Arabia, starting at noon on Monday.
A spokeswoman said it was unclear if the suspension would be extended.
Qatar Airways flies to nine cities in Saudi Arabia.
Qatar's flag carrier has not yet said if there would be changes to flights to cities such as Dubai, Abu Dhabi, and Cairo.
Dubai's Emirates and Abu Dhabi's Etihad Airways are suspending all flights to and from Doha, starting Tuesday morning.
Emirates, in a statement on its website, said its flights to and from Doha on Monday will operate as normal.
Its last flight from Dubai to Doha will depart as EK847 at 02:30am on Tuesday. The last flight from Doha to Dubai will depart as EK848 at 3:50am on Tuesday.
Etihad Airways' last flight from Abu Dhabi to Doha will depart as EY391 at 9:35pm, while the last flight from Doha to Abu Dhabi will depart as EY398 at 10:50pm on Monday, the airline said in a statement.
Both airlines are offering full refunds on unused tickets and free rebooking to alternate cities to customers booked on flights to and from Doha.
The carriers operate four daily return flights to Doha.
FlyDubai, a Dubai-based budget carrier, said it is cancelling its flights to Qatar beginning on Tuesday.
Air Arabia, a Sharjah-based carrier, said its last outbound flight from Sharjah to Doha will depart at 6:30pm on Monday, while the last inbound flight from Doha to Sharjah will depart at 7:25pm local time.
Saudi Arabian Airlines (Saudia), in a Twitter post, said it has cancelled all flights to Qatar from Monday morning onwards.
Gulf Air, Bahrain's national carrier, said its daily service between Manama and Doha will be suspended until further notice. Its last flight from Bahrain to Doha, GF530, will depart at 8:55pm and its final flight from Doha to Bahrain, GF531, will depart at 10:40pm local time on Monday.
Egypt's flag carrier, Egypt Air, has delayed its flights to and from Doha on Monday. The country's ministry of aviation said it will "halt all flights between Egypt and Qatar and close off Egyptian airspace to Qatari aircrafts that seek to land or pass through" beginning on Tuesday at 04:00GMT.
At the time of publishing, it was not clear whether airlines of the Maldives, which also joined the measures against Qatar, planned to suspend flights.
Its main opposition party, the Maldivian Democratic Party (MDP), in a statement warned any restriction "will cause huge disruption to the tourism sector".
What are the likely implications of the new restrictions?
Many analysts and experts have said the current travel disruptions are "unprecedented".
John Strickland, a UK-based aviation consultant, told Al Jazeera the announcement "came as quite a shock" to the industry.
"There's been disruptions in the region before, such as during the Gulf War," Strickland said. "Flights had to be re-routed, but I cannot think of anything comparable to the current events."
Alan Peaford, editor-in-chief of Aerospace Magazine, like Strickland, said Qatar airways will see greatest impact.
"The real problem would be if airspace closes. Not just for Qatar Airways passengers, but also for cargo, like food and fresh fruit that is flown into the country," Peaford told Al Jazeera.
He added that there are two main air routes in and out of Qatar - over Saudi Arabia and Bahrain with the latter controlling most of the Gulf air space.
"If Qatar is banned, I can't see a way out of the country for Qatari aircraft," he added.
Saj Ahmad, an analyst with London-Based Strategic Aero Research, told Khaleej Times that the "damage here isn't a one-way street".
He said that airlines "like Emirates, FlyDubai and Etihad out of Abu Dhabi will end up reeling from the sudden collapse of traffic rights".
The long term-effects "are far from clear", Ahmad said. "This has the potential to be a long and drawn-out affair."
Source: Al Jazeera and news agencies