Flag off

Flag Off or 'Flagged Off means official start or beginning of an event or undertaking. In this a piece of cloth, usually rectangular in size, and of distinctive color and design, is used as a symbol, standard, signal, or emblem and waved.
It is an idiomatic expression indicating the commencement of some event- usually involving travel or movement. Such an event is either an expedition, a race, or a rally. Mostly it is a checkered flag of black and white or a flag of single color (any color) with or without emblem or signage of the event printed on it. As a ceremonial beginning often involves waving of a flag by a dignitary to signify the formal commencement of an event, it's called flag off. In naval or maritime context, a maritime flag or a naval ensign may be waved to signify the start of an expedition. On the other hand, for stationary events, such as a sporting tournament, political summit, literary meet, etc. the equivalent expression used is kick-off.
Significance.
Even though the word 'Off' often stands for a negative meaning, 'Flag off' is used to mean that somebody gave the orders to start something like a 'race'. One of the most famous flag off was at the Formula 1 competition, when the first world championship race was held at Silverstone race track in England on May 13, 1950. A similar significant flag off event happened when the then Railway Minister Mamata Banerjee flagged off India's first ever point-to-point non-stop train, the Sealdah-New Delhi Duronto Express, from the Sealdah station in Kolkata on January 20, 2013. 