Gary said Michael, nicknamed Little Mick, made a late decision to travel independently to the World Cup in Boston and did not share detailed plans of his flights, accommodation or match arrangements.
He added: “He always meets up with friends, Leeds friends, but also England fans.”
Michael is an experienced traveller who often watches football overseas, as well as following Leeds United around the country.
He usually keeps in contact with family and friends by text message or by posting updates of grounds he visits on Facebook.
The retired trade union official has been a fan of Leeds United since the 1960s and attended their matches around the world.
Gary has reported Michael missing to West Yorkshire Police, who visited his home in Adel, west Leeds, to confirm he had not returned to the property.
Interpol have also begun attempts to try and find him. Spanish police and the British consulate have also offered assistance.
