MELBOURNE, May 17 (Xinhua) -- The world's biggest plane, the Antonov An-225 Mriya, left Australia on Tuesday with the pilots thanking Perth residents for their warm hospitality and public response to the mega aircraft.

The Ukrainian-built plane took off from Perth Airport slightly later than scheduled at 6 a.m. local time, and was farewelled by hundreds of aviation enthusiasts.

The giant cargo plane, which can weigh up to 600 tons, attracted almost 20,000 onlookers when it landed in the Western Australian capital on Sunday.

In a trip that spanned three continents, the Antonov completed its delivery of a 117-ton generator to a WA mining resource client after leaving the Czech Republic late last week.

It stayed in Perth for two days, and is now bound for Italy with a 26-ton rotor on-board.

This morning's spectacle was far less visible than the landing,  with plane taking off well before sunrise.

However, one plane spotter said it was no less impressive.

"It was amazing seeing it rotate off the runway and we are also listening to the air traffic control," the onlooker told Perth radio, while watching the plane taxi around the runway.

"The pilots in their last message to Perth Air Traffic Control,  before they handed off to Melbourne Air Traffic Control, said they wanted to thank Perth for their hospitality and kindness."

Perth residents were warned that the Antonov could create traffic problems on main roads similar to those seen on Sunday in the lead-up to its arrival.

Motorists and air passengers were told to allow for extra time to travel to and from the airport due to possible delays.

On Sunday night, the six-engine plane unloaded the massive generator -- the heaviest cargo ever carried over such distance --  using a special technique known as the "elephant kneel."

Around 55 people helped unload the plane using this method, which involves lifting up the cockpit and then employing a series of ramps and cranes to remove the cargo.