A pre-flight safety briefing (also known as a pre-flight demonstration, in-flight safety briefing, in-flight safety demonstration, safety instructions, or simply the safety video) is a detailed explanation given before take-off to airline passengers about the safety features of the aircraft they are aboard. Aviation regulations do not state how an airline should deliver the briefing, only that ‘The operator of an aircraft shall ensure that all passengers are orally briefed before each take-off’. As a result, and depending on the in-flight entertainment system in the aircraft, as well as the airline's policy, airlines may deliver a pre-recorded briefing or provide a live demonstration. A live demonstration is performed by one or more flight attendants standing up in the aisles, while another flight attendant narrates over the public address system. A pre-recorded briefing may feature audio only, or may take the form of a video (audio plus visual). Pre-flight safety briefings typically last two to six minutes. In consideration for travelers not speaking the airline's official language and for the passengers with hearing problems, the video may feature subtitles, an on-screen signer, or may be repeated in another language. Some safety videos are made using three-dimensional graphics. Other videos were made to be humorous, or feature celebrities, or were based on popular movies. Many safety videos were uploaded to YouTube. The flight attendant featured in a Delta Air Lines video from 2008 has become an internet celebrity known as Deltalina. The current (as of 2021) British Airways safety video, featuring several comedians, actors and other celebrities such as Rowan Atkinson, Gordon Ramsay and Gillian Anderson, is of humorous character and seeks to raise funds for the Comic Relief charity. In an emergency, flight attendants are trained to calmly instruct passengers how to respond, given the type of emergency. Required elements Airlines are required to orally brief their passengers before each take-off. This requirement is set by their nation's civil aviation authority, under the recommendation of the International Civil Aviation Organization. All airline safety videos are subtitled or shown secondarily in English as it is the lingua franca of aviation. Sometimes a video briefing is subtitled with the primary language of the country the airline is based in or the language of the city where the plane originates or flies to. This is up to the airline, but most (if not all) elect to do this through a safety briefing or demonstration