Quiet supersonic flight: how the FAA proposal could revive faster-than-sound travel

The US Federal Aviation Administration has proposed allowing supersonic airliners to fly over American cities, provided they are quiet enough, Ars Technica reports. The plan would replace a decades-old ban on faster-than-sound flight over land with a standard based on how much noise reaches the ground, potentially reopening a chapter of aviation that has been effectively closed since the era of Concorde.

To understand why the proposal matters, it helps to recall the sonic boom. When an aircraft flies faster than the speed of sound, it compresses the air ahead of it into shock waves that spread out and reach the ground as a sudden, loud bang. Over populated areas, repeated booms were considered disruptive enough that the United States prohibited civil supersonic flight over land in the early 1970s.

That ban is the reason Concorde, the famous Anglo-French supersonic jet, spent most of its career flying supersonic only over oceans, cruising at ordinary speeds over land. The restriction, combined with high costs and limited routes, helped confine supersonic passenger travel to a niche that eventually disappeared when Concorde was retired in 2003.

The key shift in the FAA's proposal, according to Ars Technica, is moving from a rule based purely on speed to one based on noise. Under the current regime, flying faster than sound over land is banned outright regardless of how loud the aircraft actually is. The new approach would instead permit supersonic flight as long as the noise reaching people below stays under a defined threshold.

This change is made possible by advances in aircraft design aimed at softening the sonic boom into something more like a muffled thump. By carefully shaping an aircraft's body, engineers can spread out the shock waves so they arrive at the ground less abruptly, reducing the sharp bang to a quieter sound. This concept, often called low-boom or quiet supersonic design, has been the subject of experimental programmes in recent years.

For aircraft makers and startups betting on a supersonic revival, a noise-based rule would be a significant opening. Several companies have been developing supersonic passenger jets, and the prospect of flying quickly over land, not just over water, greatly expands the routes on which such planes could be commercially viable, since many lucrative journeys cross continents rather than oceans.

Still, important caveats apply. A proposal is not a finished rule; regulatory processes typically involve public comment, technical review and revision before anything takes effect. The specific noise threshold that regulators set will be crucial, as it determines how quiet an aircraft must be and therefore how hard the engineering challenge remains.

There are also practical and commercial hurdles beyond the regulatory one. Building a supersonic jet that is quiet, fuel-efficient and economical to operate is a formidable task, and supersonic flight tends to burn more fuel per passenger than conventional airliners, raising questions about cost and environmental impact that manufacturers will have to address.

The environmental dimension is likely to feature prominently in the debate. Aviation is already under scrutiny for its contribution to carbon emissions, and faster aircraft that consume more fuel per seat will draw questions about how a supersonic revival fits with efforts to reduce the sector's climate footprint, alongside concerns about emissions at high altitude.

For now, the proposal marks a notable moment: a regulator signalling that the long-standing overland ban could give way to a performance-based standard shaped by technology. Whether that translates into passengers boarding supersonic flights again will depend on the final rules, the engineering, and whether the economics can be made to work — but the door that closed with Concorde has, at least, been nudged open.