A 16-year-old schoolboy who is on a quest to become the youngest person to fly around the world solo landed his small plane in Kenya’s capital, Nairobi, on Wednesday.

Mack Rutherford, who has British and Belgian nationality, started his journey near the Bulgarian capital Sofia in March and is looking to clinch a Guinness World record held by compatriot Travis Ludlow, who was 18 when he completed a circumnavigation last year.

“I’m hoping, with this journey, to inspire young people to follow their dreams,” Rutherford said after clambering out of his two-seater single-prop ultralight aircraft at Wilson Airport...