A Malaysian Airlines plane headed for Colombo, Sri Lanka, made an air turn back after circling the Straits of Malacca for two hours.

According to aircraft tracking websites, Flight MH179 had flown in circles (known as a holding pattern) over the ocean west of Pulau Ketam since about 11.30pm.

"MH179 is returning to Kuala Lumpur after two hours of fuel burn to reduce landing weight," Flightradar24 tweeted at 1.30am.

It then landed safely in KLIA 20 minutes later.

It is currently unknown what had caused the turn back.

In aviation, a holding pattern is a racetrack-shaped flight path that is flown over repeatedly by the same aircraft.

It is typically used by aircraft to maintain its location while waiting for permission to land at a congested airport.

It is also used by some aircraft to burn fuel until it is light enough to make a safe landing if its journey is cut short, including Boeing 737-800s such as the one used to fly the MH179 route.

This because these aircraft lack the equipment to reduce weight by dumping excess fuel into the sky.

In aeronautics, holding is a circling maneuver designed to delay an aircraft already in flight while keeping it within a specified airspace.

It is most commonly performed when airports are congested and there is no space to land.

According to MAS' website, MH179 departed from KL International Airport at 11.27pm and was supposed to arrive in Colombo at 12.18am local time.

Word about MH179's situation was had spread quickly through social media, with many expressing relief after the plane had safely landed.

Please land safely this timee pleaseeee. #MH179 pic.twitter.com/rmQ8Xjd58m

— dieba rahman (@dibabolart) May 9, 2015

It feels good to know #MH179 is now safely landed at KLIA. Alhamdulillah.

— Nazmi (@nazmihaq) May 9, 2015

Thank god! I don't think we would have been ready for another tragedy. #MH179 welcome home. https://t.co/f1KKivLP5F

— MB™ - 32 (@melakaboy) May 9, 2015