John Varun's daredevil stunt in the Dishoom

John Abraham and Varun Dhawan take actions in next level

Varun Dhawan has been getting some rave reviews for his new film, Dishoom. Co starring John Abraham and Jacqueline Fernandez, the film has some great stunts.
One of them has Varun and John clinging dangerously to a helicopter.
So how they did actually do that stunt