CHICAGO -- 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."