The 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 inflight 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 a flight attendant/s standing up in the aisle/s, 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. Cebu Pacific choreographed the entire demonstration to Lady Gaga’s “Just Dance” and Katy Perry’s “California Gurls” as an experiment during one of their flights. The flight attendant featured in the most recent Delta Air Lines video has become an internet celebrity known as Deltalina. The current (as of 2018) 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 nations 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 and sometimes it’s 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 delivered to all passengers at the same time. A safety demonstration typically covers all these aspects, not necessarily in this order:

demonstrating or telling passengers that the safety card shows the brace position and must be adopted on hearing the “Brace Brace” command during an emergency landing. (sometimes called the safety position) (this is not required in the United States and certain other countries and is mostly included in European regions)
the use of the seat belt. Some airlines recommend or require that passengers keep their seatbelt fastened at all times in case of unexpected turbulence.
the requirement that passengers must comply with lighted signs, posted placards, and crew members instructions (Generally only included in safety demonstrations on Australian, New Zealand, and American carriers as the CASA (AU), CAA (NZ) and FAA (US) require it to be stated). Most other airlines only include the seatbelt and no smoking signs.
the location and use of the emergency exits, evacuation slides and emergency floor lighting
that all passengers should locate their nearest exit, which may be behind them
the requirements for sitting in an emergency exit row (varies by country and airline). In the United States it must also be stated that exit row passengers may be required to assist the crew in an evacuation.
that all passengers must leave all carry-on bags behind during an evacuation
some demonstrations also mention that high heeled shoes and/or any sharp objects must be removed (this is to ensure that evacuation slides are not punctured)
the use of the oxygen mask (not included on some turboprops which do not fly high enough to need supplemental oxygen in a decompression emergency) with associated reminders:
that the passenger should always fit his or her own mask on before helping children, the disabled, or any persons requiring assistance
that even though oxygen will be flowing to the mask, the plastic bag may not inflate (required in the United States after a woman fatally removed her mask thinking it was not working). Some planes such as the Boeing 787 do not include plastic bags in the oxygen masks.
if applicable to the aircraft in question, that the passenger must pull down on a strap to retrieve the mask
the location and use of the life vests, life rafts and flotation devices (not always included if the flight does not overfly or fly near vast masses of water although is required by the FAA (US) on any aircraft equipped with life vests)
the use of passenger seat cushions as flotation devices (typically only included on aircraft that do not provide life vests)
restrictions enforced by law and/or airline policies, which typically include…
that smoking is not allowed on board, including in the lavatories (though most airlines now refer to them as restrooms). Some airlines, including the US on all Domestic flights and international flights going to and from the US, also ban electronic cigarettes).
on flights where smoking was permitted a reminder was often issued that smoking is only acceptable in smoking sections but nowhere else on board
that US federal law prohibits tampering with, disabling or destroying lavatory smoke detectors
that the use of mobile phones is not allowed during flight, unless placed in “airplane mode” or the wireless capability is turned off
that laptops and other electronics may only be used once the aircraft is at cruising altitude and the Captain turns off the fasten seat-belt signs.
Some airlines may require passengers to also turn off all devices during taxi, take-off, and landing (such as Kenya Airways and Malaysia Airlines) in addition to having these devices set to Airplane mode
if present, most airlines may also require passengers to unplug these devices from charging ports during these times
If the passenger loses an electronic device under a seat, the passenger should not adjust the seat as this may damage the device or injure the passenger. Instead, the passenger should notify the flight attendants to locate the device safely.
that passengers must ask a flight attendant prior to using electronics
actions required of passengers prior to takeoff
that seatbacks and tray tables should be in their upright and locked position, headrest stowed, and carry-on luggage stowed in the overhead locker or underneath a seat prior to takeoff
and in most cases, if seated next to a window, the window blinds must be raised for take off and landing. The Boeing 787 does not have window blinds as the windows can be dimmed, however, the windows may sometimes not be dimmed during take off and landing.
to review the safety information card prior to takeoff or to follow along during the demonstration.

History of Pre-Recorded Safety Videos
The approval of using video for pre-flight safety demonstrations was originally included in FAA Advisory Circular 135-12, released on October 9, 1984. This is further explained in FAA Advisory Circular 121-24C, which stated that video offered several advantages over the standard manual demonstration, but only provided that the airliner has the required video and sound systems to exhibit the video properly.

1980s and early 1990s
As in-flight video entertainment systems were beginning to see mainstream introduction, airlines began producing safety demonstration videos to be used in lieu of or in tandem with a manual demonstration performed by one or more flight attendants. Notable examples include Trans World Airlines, Pan Am, and Northwest.

Early videos from the late 1980s sometimes omit warnings about electronic devices, as it was less of a concern at the time. Since smoking was still acceptable on many airliners, these videos feature antiquated reminders about smoking on board, including acceptable locations to do so and a command to stop smoking should the oxygen masks be deployed.

Videos of this era often use 2-dimensional animation or very primitive 3D computer generated imagery to illustrate elements of the demonstration. While animation is usually used sparingly, some videos are fully animated (usually in 3D), such as ATA’s circa-1994 safety video.

When videos of this time were captioned, it was usually only captioned in the language already being spoken on the audio track. Captions were almost always included by way of standard television closed captioning. If not, the captions are recorded into the video and mimic closed captioning by use of black boxes surrounding white text. Bilingual videos typically had the primary lanuage’s instructions repeated immediately afterward, but almost never had the secondary language captioned.

Arguably, elements of the demonstration were either overexplained, underexplained, or poorly described during this time. For instance, TWA’s safety video mentioned a “slight burning odor” when oxygen masks are in use. Most demonstrations were also lacking in their explanation of electronic device policies as portable electronic devices were only beginning to become a concern.

Videos were typically designated to a specific model of aircraft but shared certain assets between videos produced by the same airline, including film recorded on a completely different aircraft. This practice continues to the modern day, although it is variably less prevalent than during the 1980s and 1990s.

Late 1990s and Early 2000s
By this point, airlines had found a refined format for their videos. Most videos, though produced differently, kept the same basic script with the same points. For instance, the Delta Air Lines safety video from 2000 and 2001 quoted one of their early 90s videos verbatim for most of the runtime.

Electronic device policies were also updated to include that cellular phones and other radio-based electronics are not permitted to be used at any time.

Effectiveness
Research conducted at the University of New South Wales Australia questions the effectiveness of these briefings in conveying key safety messages for passengers to recall and act upon in an emergency. In one study, a range of pre-recorded safety briefings were tested. One safety briefing contained humor, another was void of humor (said to reflect a standard style briefing), and another used a celebrity to sell the importance of the safety briefing and the messages contained within. Not long after being exposed to the briefing, individuals recalled approximately 50% of the key safety messages from the briefing featuring the celebrity, 45% from the briefing containing humor, and 32% from the briefing void of both a celebrity and humor. Two hours post exposure to the pre-flight safety briefings, recall decreased on average by 4% from the original levels across all conditions.

Source from Wikipedia