A Swiss research group landed their solar powered aircraft successfully after completing an overnight flight Thursday. The plane was able to fly at night as it was able to store energy it was able to gather during the day.

The Solar Impulse, a four-engine plane, took off from Switzerland’s Payerne airbase early Wednesday and returned at dawn Thursday.

“It was unbelievable, success better than we expected,” the plane’s pilot, Andre Borschberg, a Swiss air force veteran, told Reuters television. “We almost thought to make it longer, but we demonstrated what we wanted to demonstrate so they made me come back,” he said.

“This is a highly symbolic moment,” said Bertrand Piccard, initiator and president of Solar Impulse, in a statement.

“I’ve been a pilot for 40 years now, but this flight has been the most incredible one of my flying career,” Borschberg said. “Just sitting there and watching the battery charge level rise and rise, thanks to the sun.”

He added that he had flown the entire trip without using any fuel or causing pollution, flying the aircraft to an altitude of 8,654 meters while achieving a top ground speed of 68 knots.