Reintroducing commercial supersonic transport (SST) aircraft into the global aviation fleet could have significant noise and climate impacts by 2035, according to a new study by the International Council on Clean Transportation (ICCT). The paper analyzes the landing and takeoff (LTO) noise, sonic boom, and CO₂ implications of introducing 2,000 new commercial supersonic transport (SST) aircraft serving 500 cities in 2035, a scenario envisioned by a prominent SST startup.

Global sonic boom incidence. Source: The ICCT.

A 2,000-strong supersonic fleet would translate to approximately 5,000 flights per day at 160 airports located predominately in Europe, North America, the Middle East, Asia, and Oceana. The two busiest airports, Dubai and London Heathrow, could each see more than 300 operations per day. Other airports that could see 100 or more daily SST LTOs include Los Angeles, Singapore, San Francisco, New York-JFK, Frankfurt, and Bangkok.

Other key findings of the work include:

• 87% of flights are expected to be international, with about one third being transoceanic.

• The aircraft could double the area around airports exposed to substantial noise pollution compared to existing subsonic aircraft of the same size.

• Canada, Germany, Iraq, Ireland, Romania, Turkey, and parts of the United States would experience frequent sonic booms; the most heavily impacted regions could be exposed to between 150 and 200 incidents per day, or up to one boom every five minutes over a 16 hour flight day.

• The fleet would emit an estimated 96 million metric tons (MMT) of CO₂ per year—comparable to the combined annual emissions of US carriers American, Southwest, and Delta in 2017, and more than three times the emissions of Lufthansa Group, Europe’s largest combination of carriers, in the same year. The fleet of SSTs would emit an additional 1.6 to 2.4 gigatonnes of CO₂ over the aircrafts’ 25-year lifetime. This equals about one-fifth of a proportional carbon budget afforded international aviation under a 1.5 degree Celsius climate trajectory.

• To boost the public acceptability of SSTs, aspiring manufacturers should commit to meeting existing standards for new subsonic aircraft and to support new supersonic noise standards that would mandate low boom technology.

Three US-based startups are working to develop new supersonic transport aircraft, including a 55 seat commercial jet. Since 2016, advocates of supersonic flight have pushed to lift existing bans on overland flight in the US despite the objections of environmental and public health groups. Today, there are effectively no environmental standards for supersonic aircraft. The Trump administration, which favors permissive standards for SSTs, has clashed with Europe about their potential noise impacts.

International regulators will meet in Montreal for two weeks starting 4 February to discuss whether to apply existing subsonic standards to SSTs or to develop new, more lenient SST standards.

Greenhouse gas emissions and air pollution from commercial aircraft are rapidly increasing, the ICCT noted. Treated as a country, the global aviation sector would have been the sixth-largest source of CO₂ from energy use in 2015, emitting more than Germany. CO₂ emissions from global aviation hit an all-time high of 859 MMT in 2017, up 10% from 2015 levels.

Resources

• Dan Rutherford, Brandon Graver, and Chen Chen (2019) “Noise and climate impacts of an unconstrained commercial supersonic network”