Three of the world’s biggest airlines have admitted some of their planes have cameras installed on the backs of passenger seats.

American Airlines, United Airlines and Singapore Airlines have new seat-back entertainment systems that include cameras.

They could also be on planes used by other carriers.

Companies that make the entertainment systems are fitting them with cameras to offer passengers options such as seat-to-seat video conferencing, according to an American Airlines spokesman.

But American, United and Singapore all say they have never activated the cameras and have no plans to use them.

New Boom Supersonic airliner – in pictures Show all 10 1 /10 New Boom Supersonic airliner – in pictures New Boom Supersonic airliner – in pictures A model of the Boom Overture, designed to carry 55 passengers at more than twice the speed of sound Boom Supersonic New Boom Supersonic airliner – in pictures Boom Supersonic has obtained funding of $100m (£79m) for the next stage of its project to create a commercial aircraft, known as Overture, planned to fly at more than twice the speed of sound, with a range of 5,180 miles Boom Supersonic New Boom Supersonic airliner – in pictures A half-size prototype, known as XB-1, is set to fly later in 2019. The firm claims it is “history’s first independently developed supersonic jet and the fastest civil aircraft ever built” Boom Supersonic New Boom Supersonic airliner – in pictures Once the Boom Overture is in commercial service, routes such as London to Mumbai, Manchester to Dallas-Fort Worth and Edinburgh to Vancouver will take around four hours – better than halve the time of conventional jets Boom Supersonic New Boom Supersonic airliner – in pictures Virgin Atlantic has options for 10 of the aircraft. Sir Richard Branson's airline unsuccessfully fought for the right to keep Concorde flying Boom Supersonic New Boom Supersonic airliner – in pictures The project to build a viable supersonic transport (SST) is aiming for a cabin barely half the size of Concorde: just 55 seats, compared with 100 on the Anglo-French jet. But the three-engine Boom aircraft will fly further, more economically and less noisily, with a sonic boom “at least 30 times quieter” than Concorde Boom Supersonic New Boom Supersonic airliner – in pictures At landing and takeoff, the company says: “Overture will be as quiet as the subsonic aircraft flying similar routes today.” But in July 2018, the International Council on Clean Transportation warned: “Emerging SSTs are likely to fail current and perhaps historical landing and take-off noise standards.” Boom Supersonic New Boom Supersonic airliner – in pictures The organisation also predicts supersonic aircraft will consume between five and seven times as much fuel per passenger relative to comparable subsonic aircraft. Concorde used about as much fuel to fly 100 passengers as an Airbus A380 does on the same distance with five times as many people onboard. The supersonic jet flew for Air France and British Airways, but was permanently grounded in October 2003 as high fuel costs rendered the economics hopeless. Since then all commercial air travel has been subsonic Boom Supersonic New Boom Supersonic airliner – in pictures Boom says: “From 1903 to 1976, the speed of passenger aviation increased relentlessly from 7mph to Mach 2. Then something broke. “Over the last 40 years, not only have we failed to generate further speed increases, we’ve lost supersonic capability.” “Supersonic flight removes a critical barrier to new business relationships, new cultural experiences, and more time with loved ones.” The company is even claiming health benefits, saying: “Sitting in one place for too long causes blood circulation to slow, which can cause serious problems such as deep vein thrombosis.“ Because supersonic flights are shorter than subsonic ones, passengers spend less time sitting still.” Boom Supersonic New Boom Supersonic airliner – in pictures Investors in the Colorado-based company include the Emerson Collective, headed by Laurene Powell Jobs – widow of Apple’s former chief executive, Steve Jobs. “This new funding allows us to advance work on Overture, the world’s first economically viable supersonic airliner,” said Blake Scholl, founder of Boom Supersonic. Prices are planned to be “similar to today’s business class”. One immediate problem: supersonic flight is currently banned over the United States. Boom will focus on routes that are primarily overwater. The company cites routes such as San Francisco to Tokyo – though at 5,155 miles the journey will require a refuelling stop, probably in Anchorage Alaska Boom Supersonic

A passenger on a Singapore flight tweeted a photograph last week of the seat-back display, prompting other air travellers to voice concerns about their privacy at 30,000ft.

Vitaly Kamluk, who photographed the camera on his flight, suggested that carriers should cover the lenses with stickers and said it would be easy for airlines to monitor passengers with them.

“The cameras are probably not used now,” he tweeted. “But if they are wired, operational, bundled with mic, it’s a matter of one smart hack to use them on 84+ aircrafts and spy on passengers.”

American Airlines spokesman Ross Feinstein said cameras were in “premium economy” seats on 82 Boeing 777 and Airbus A330-200 jets.

“Cameras are a standard feature on many in-flight entertainment systems used by multiple airlines,” he said.

British Airways told The Independent none of its planes had cameras on seat backs.

Singapore spokesman James Boyd said cameras were on 84 Airbus A350s, Airbus A380s and Boeing 777s and 787s.

But a United spokeswoman repeatedly told reporters on Friday that none of its entertainment systems had cameras – before apologising and saying that some did.

Delta did not respond to questions about some of its entertainment systems, which appear to be identical to those on American and United.

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The airlines stressed that they did not add the cameras – saying manufacturers embedded them in the entertainment systems.

American’s systems are made by Panasonic, while Singapore uses Panasonic and Thales, according to airline representatives. Neither Panasonic nor Thales responded immediately to requests to comment.