London to New York may again be possible in under 4 hours after the US-based airline struck a deal for 15 ultrafast jets. Regular commercial supersonic flights have not been seen since 2003. United Airlines announced on Thursday that it was planning to buy 15 supersonic jets from Denver-based aerospace company Boom Supersonic, reviving the kind of high-speed air travel not witnessed since the demise of Concorde almost two decades ago. “We’re the first US airline to sign an agreement for Boom’s Overture airliners,” United said on Twitter, adding the planes would be ready for take off in 2029.