To celebrate the 40th birthday of her husband John Lennon, and the fifth of her son Sean, Yoko Ono hired an aircraft pilot to skywrite a message in the sky above the Dakota.
Lennon and Ono had been inside the Hit Factory studio since the previous day, working on Double Fantasy. Yoko gave him a tie she had knitted, and later on presented him with a box containing a diamond and ruby US flag brooch, which he pinned to the tie.
By midday dozens of fans were assembled outside the Dakota, not realising Lennon wasn't there. Two women brought a sign made out of sheets which read Happy Birthday John Lennon, which they spread on the pavement so it would have been visibile from his apartment.
Shortly afterwards Lennon arrived back from the Hit Factory. They were driven in a limousine to the Dakota and went inside without many of the fans noticing.
At around 5pm the skywriting began over Central Park, and the crowds of fans ran to the park to try to get a glimpse of Lennon. They saw instead Sean and assistant Fred Seaman standing on the roof of the Dakota, but Lennon was asleep and missed the show.
The message read: "Happy Birthday John & Sean - Love Yoko", and was written nine times in the sky. The occasion became a major news item on US television.
