The UN's top court will rule Tuesday in a bitter feud between Qatar and four rival neighbours which imposed an air blockade against Doha after accusing it of backing radical Islamists and Iran.
The decision covers a key part of the acrimonious standoff that erupted three years ago between Qatar and Bahrain, Egypt, Saudi Arabia and the United Arab Emirates.
The four other states are asking the International Court of Justice (ICJ) to quash a decision by the world civil aviation body in favour of Qatar over sovereign airspace.
The International Civil Aviation Organisation (ICAO) in 2018 ruled it had the jurisdiction to handle a dispute brought by Qatar, which accused its neighbours of violating a convention that regulates the free passage of its passenger planes through foreign airspace.
But the four allies disagreed, saying the ICAO was not the right body to judge in the dispute and that its decision to do so was "manifestly flawed and in violation of fundamental principles of due process and the right to be heard."
They are now asking the Hague-based ICJ's judges to declare the ICAO ruling "null and void and without effect."
Saudi Arabia, Bahrain, the UAE and other allies severed ties with Qatar in June 2017, accusing the gas and oil-rich country of backing radical Islamists and Iran.
They imposed wide-ranging punitive measures including banning Qatari planes from their airspace, closing Qatar's only land border with Saudi Arabia and expelling Qatari citizens.
Doha strongly denies the allegations.
The countries justified the moves against the Gulf peninsula state saying it was their sovereign right to protect their national security.
Qatar fiercely rejected the claims that it had violated a series of agreements inked with its neighbours in 2013 and 2014 aimed at settling years of diplomatic rancour.
Last year the ICJ -- set up in 1946 to rule in disputes between UN member states -- rejected a request by the UAE to take special measures against Qatar, after Doha won a case at the ICJ in 2018 over alleged discrimination against its citizens.
Doha in June again accused the Saudi-led alliance of refusing to engage with efforts to resolve the crisis that it said were backed by the United States.