The UAE has submitted a complaint to the International Civil Aviation Organisation over the Qatari interception of two UAE-registered civilian aircraft last week.
The General Civil Aviation Authority (GCAA) has submitted a complaint as per article 54 of the Chicago Convention, the state news agency Wam reported.
"These aggressive actions by Qatar against UAE civilian aircraft are considered as deliberate violations of international covenants and conventions governing civil aviation and are a threat to the safety of civil aviation,” said Saif Al Suwaidi, the director general of the GCAA.
Last Monday, two Qatari fighter jets came within 214 vertical metres of a UAE-registered Airbus. The plane was on a scheduled flight to Europe when the jets approached it from the north and circled behind it. It took place over international waters, 18 nautical miles (33 kilometres) from the Qatari coast.
In a separate incident that day, Qatari aircraft approached a UAE-registered helicopter.
The actions put crew and passengers at risk, said Mr Al Suwaidi.
“The UAE outright rejects these acts,” he added.
The GCAA previously filed an earlier complaint about the Qatari interception of two civilian aircraft on January 15.
Qatari officials claimed that former allegations were made to cover up UAE military aircraft violations of its airspace on December 21 and January 3, the Associated Press reported. The UAE denied these allegations.
Qatari fighter jets have approached UAE military aircraft on three separate occasions.
Brig Gen Helal Al Qubaisi reported that a UAE Twin Otter aircraft was approached on January 3, a C-130 cargo plane was approached on January 12 and an F-16 was approached on December 27. The general condemned the manoeuvre as an “aggressive act” and said the UAE military was using alternative routes over Saudi Arabia. UAE civilian aircraft had not changed their routes.
Aviation expert Saj Ahmad, chief analyst at StrategicAero Research, said "the complaints are indeed very serious".
He said the ICAO has little mandate to enact and forcible action on either party.
"Right now, that is independently orchestrated by whomever has ownership of an airway or airspace, much in the same way that Saudi Arabia has allowed Air India to fly direct to Israel, but not afforded the same to Israeli airline El Al."
But he said there is an urgent need to ensure there is no repeat of the incursions that have allegedly taken place in recent weeks.
"About the only good thing that can come about out of these complaints and counter-complaints is that the two sides will have to at some point sit down and talk this through," he said.
"The last thing anyone wants is a knee-jerk reaction or military confrontation that jeopardises commercial traffic in an already-congested region."
Saudi Arabia, Bahrain, Egypt and the UAE cut all ties with Qatar in June 2017, accusing it of supporting extremism and interference in the internal affairs of other states.