The world's only solar-powered aircraft Solar Impulse-2 was flying over Chittagong Hill tracts in Bangladesh on its way to Myanmar this afternoon, sources at the Swiss Embassy said.

The Si2 entered Bangladesh air space around 1:30pm and crossed over Bangladesh around 3:00pm on its way to Mandalay in Myanmar (Burma) after taking off from Varanasi in the morning.

This is the fourth leg in the plane’s historic bid to fly around the world powered only by the Sun's rays.

Swiss pilots Bertrand Piccard and André Borschberg, who are trying to make history by flying a solar-powered plane, started the first round-the-world flight on March 9 from Abu Dhabi (UAE).

They are expected to return to Switzerland at the end of July or early August.

According to a press release of the Embassy of Switzerland in Bangladesh, this solar-powered aircraft is designed to remain airborne day and night without using a drop of fuel.

The plane's exceptional aerodynamic performance and energy efficiency (three times greater than commercial aircraft) make this possible. A team of technicians and scientists from the Swiss Federal Institute of Technology Lausanne (EPFL) worked together on this ground-breaking project, the statement reads.

This first round-the-world solar flight involves landings in Oman, India, Myanmar and China before crossing the Pacific Ocean. It will then stop-over in the United States and finally cross the Atlantic Ocean, heading for Southern Europe or North Africa and to its point of departure.