The 40-year-old man worked for the Vietnam Airlines Engineering Company, a subsidiary of Vietnam Airlines.
He was checking a Vietnam Airlines plane which was preparing to leave Hanoi for Vinh in central Vietnam when a bolt of lightning struck the right wing of the plane and knocked him out.
He died on the way to hospital.
Tran Hoai Phuong, director of the Northern Airports Authority, said the tragedy occurred at 6:05 p.m.
The official Facebook page of Vietnam's aviation ground crew carried the message, "To our brother, may your soul rest in peace."
Lightning strikes occur occasionally at airports in Vietnam, but this is the first time a worker has been killed.
A Noi Bai airport spokesperson said the airport has a lightning protection system of international standard.
In 2016 Tan Son Nhat International Airport in HCMC was forced to close down a runway after it had been damaged by lightning.