Zhang Bo waves to family members and friends after landing at an airport in Chicago, the United States, on June 9, 2019. (Xinhua/Wang Ping)

CHICAGO, June 9 (Xinhua) -- After flying 68 days and making 50 stops, 57-year-old Bo Zhang completed his second around-the-world flight and landed in Chicago on Sunday morning.

Before landing, Zhang circled around a small airport, an hour's drive southwest of Chicago, four times at low altitude to express his excitement.

On April 2, Zhang kicked off the flight in the same airport in Chicago. In 68 days, he flied through 21 countries in three continents and over three oceans, with total mileage reaching 41,000 kilometers.

As the airplane he flied is piston propelled and has no pressure cabin with limited endurance and flying altitude, "the challenges I encountered this time are much more than when I did the first around-the-world flight," Zhang told Xinhua in an interview. "I have experienced all hardships, expected and unexpected."

The most difficult part of the flight is over the Arctic area. "After taking off from Chicago, I directly flied northward into the Arctic Circle. Weather there was still cold in early April, when the ground temperature was 20 Celsius degrees below the zero," he said. "I was flying at an altitude of 15,000 feet, and temperature there was minus 50 Celsius."

The Diamond DA42 aircraft which Zhang Bo drove for his flight around the world lands at an airport in Chicago, the United States, on June 9, 2019. (Xinhua/Wang Ping)

As the small DA42 aircraft is not equipped with air conditioning system, Zhang donned a special kit called ocean commander immersion suit to keep warm.

When flying across the northern Atlantic Ocean from the Greenland to Iceland, Zhang encountered strong headwind, and the flight speed dropped to 110 to 120 kilometers per hour. "I realized there was no way to fly over the ocean on the day, so I turned back and landed in a small gravel airport on the east coast of the Greenland."

He got frostbite in ears when being out for two minutes checking the airplane at the airport.

High oil pressure is another difficulty Zhang has experienced. After taking off from the Urumqi Airport in Northwest China's Xinjiang Uygur Autonomous Region, he found the oil pressure of the left engine was in the red area, and immediately turned off the engine according to flight manual. "This is very challenging as well as dangerous. Fortunately, under the guidance of the control tower, I landed safely."

During the whole trip, Zhang was battling with various problems such as fuel supply, mechanical failure, and emergency maintenance and repair almost every day. But he has managed to overcome all the difficulties, be they big or small, and return safely.

"I was warmly received by overseas Chinese all the way along the journey, 99 percent of whom I did not know," he told Xinhua. "They brought me dumplings." Workers of Chinese enterprises in Kazakhstan even stayed at the airport for five hours, waiting to greet him.

Hangzhou, capital of East China's Zhejiang Province, held a watering ceremony for him. Several fire trucks have practiced for two weeks for the ceremony.

Zhang stayed for more than one month and stopped over 20-plus airports in China during the trip. "Administrations at various levels in China offered me strong support." With the support, he has cut through China from northwest Xinjiang Uygur Autonomous Region to East China's Zhejiang Province, and then turned northeast and left China from Heilongjiang Province. "I flied over the Yangtze River, the Yellow River and the Great Wall in one flight. I am so glad," he said proudly.

What made Zhang prouder is that he may contribute a bit to China's aviation history. "We have land Silk Road and maritime Silk Road. We should also have an aerial Silk Road."

Zhang Bo unloads an immersion suit from his plane at an airport in Chicago, the United States, on June 9, 2019. (Xinhua/Wang Ping)

Zhang has already started to plan for his third around-the-world flight. "There will be six planes together completing the third flight," he envisioned. "The starting and landing place will be definitely somewhere in China," he said.

Zhang made history in 2016 when he performed his first flight around the world in a propeller-driven aircraft. On Aug. 7, 2016, Zhang took off from Beijing in a TBM700 Single-engine turboprop aircraft, flew past 23 countries, measured 40,818 km and landed safely in Beijing on Sept. 24, 2016, after 44 landing points in 49 days.