Flight VN384 operated by Vietnam Airlines, with 145 passengers on board, was already one hour and 45 minutes away from Hanoi when the 10-year-old boy suffered a nosebleed. The boy was accompanied by his mother and sister.
The crew provided immediate first-aid, and subsequently decided to return to Hanoi's Noi Bai International Airport for medical assistance.
After landing, the boy was taken to a hospital in Hanoi. His health is now stable.
The plane later resumed its trip, which was delayed for four hours.
Doan Thi Kim Tho, head flight attendant, said there was no doctor on the plane and still 3.5 hours left to Japan, prompting the decision to return to Hanoi.
"We are glad to learn that the boy’s health is now stable," she said.