The recent advancement in technology breaks the barriers to communication between users and computers. The communication between humans and computers includes emotion and gesture recognition. Emotions can be recognized on the face of humans whereas gesture recognition includes hand and body gesture recognition. Fingertip detection is also part of it. Gesture recognition is the way of interaction that is used in air writing. Users can control the devices with simple gestures without touching them. It is how computers can understand human language which will reduce the interaction barriers between them. This paper discusses the different techniques that can be used for fingertip detection in air writing using machine learning