A Qantas flight has safely touched down in Sydney after the pilots issued a distress signal when an engine malfunctioned - with the nation taking a collective sigh of relief.
Dozens of emergency service vehicles dashed to Sydney International Airport on Wednesday afternoon after QF144 from Auckland, carrying 168 passengers, issued a mayday 7700 emergency call to air traffic control.
A mayday call is made when the aircraft is in a condition of being threatened by serious and/or imminent danger and is requiring immediate assistance, according to aviation expert Neil Hansford.
Once the call is issued controllers alert aviation rescue, firefighting and emergency services with details on how to respond. They also provide assistance to pilots, he added.
Meanwhile, air traffic controllers also use squawk codes, which are transponder codes used to identify planes in the airspace.
Under certain circumstances, the specific code assigned to a flight can be changed.
Flight Radar indicated the flight, travelling from Auckland to Sydney, is currently over the water
The Qantas flight on approach to the airport. It appeared to land safely just before 3.30pm
A squawk code for a flight will become 7700 in incidents when an aircraft is experiencing an emergency event, with the number then showing up on controller's screens which are tracking the flight.
The code will also be accompanied by vital information, such as the aircraft's speed and altitude.
The pilot of QF144 sparked fears after issuing a midair mayday call halfway into the just over three hour journey after it suffered the engine failure.
The jet, a Boeing 737-800, has twin engines but can still fly on just one.
As of 3.01pm, the plane had descended to 20,000ft - significantly below its planned altitude of 38,000ft. However, it landed safely around 25 minutes later.
Emergency services at the scene at Sydney Airport after a Qantas flight issues a mayday call
After its safe landing, Qantas said the mayday had been downgraded to a 'possible assistance needed'.
An alert from emergency services said: 'NSW Ambulance paramedics are responding to a May Day alert issued by flight QF144 from Auckland. The plane is due at Sydney Airport.'
An aviation expert said: 'QF144 has been on a gentle descent for 1.5 hours. At 21,000 feet currently doing 400knots.
'Normal would be 38,000 feet at about 450-480knots. This may suggest the plane is being nursed into Sydney.'
More than 100,000 people were tracking the flight on Flight Radar as it approached Sydney.
Qantas is considered one of the world's safest airlines without a fatal crash in more than 70 years.
English (United States) ·