Qatar Airways Airbus A380. Flickr/Eric Salard On Monday, the governments of Saudi Arabia, the United Arab Emirates, Egypt, and Bahrain announced they had severed diplomatic relations with Qatar.

Caught in the diplomatic crisis is the country's national airline, Qatar Airways.

The nations have said they will refuse the Qatari airline access to their airspace. But Saudi Arabia and the emirates of Abu Dhabi and Dubai happen to be some of its biggest markets.

According to Will Horton, an analyst at CAPA Centre for Aviation, Saudi Arabia is Qatar Airways' largest market. Qatar Airways' presence in Saudi Arabia is the largest of any international airline.

A Qatar Airways representative was not immediately available for comment.

The governments accuse Qatar of destabilizing the region's security by supporting the Muslim Brotherhood, ISIS, and Iran.

In a statement, the UAE's Ministry of Foreign of Affairs and International Cooperation wrote:

"In support of the statements issued by the sisterly Kingdom of Bahrain and sisterly Kingdom of Saudi Arabia, the United Arab Emirates severs all relations with the State of Qatar, including breaking off diplomatic relations, and gives Qatari diplomats 48 hours to leave the UAE. ...

"Closure of UAE airspace and seaports for all Qataris in 24 hours and banning all Qatari means of transportation, coming to or leaving the UAE, from crossing, entering or leaving the UAE territories, and taking all legal measures in collaboration with friendly countries and international companies with regards to Qataris using the UAE airspace and territorial waters, from and to Qatar, for national security considerations."

While the countries can refuse landing rights, it's unclear whether Bahrain, Egypt, or the UAE can legally ban Qatar Airways from their airspace, as they are signatories to the International Air Services Transit Agreement. Saudi Arabia is not an IASTA member country.

Over the past two decades, Qatar Airways has become one of the most influential international airlines in the world. In 2015, the consumer-aviation website Skytrax named it the best airline in the world.