United Airline’s announcement that it has placed an order for fifteen Boom Overture’s came as some sort of a shock on Thursday. While potentially opening a new chapter in the book of supersonic passenger aircraft, a lot needs to be done before the first passenger will board a United Overture. Boom still has many boxes to tick. Let’s have a look at what question marks are there.

1 – From demonstrator to Overture:

Boom Supersonic started in 2014 with a stepped development approach. First a demonstrator, then the actual supersonic passenger aircraft. The XB-1 demonstrator has been under construction since late 2019 and rolled out of assembly on October 7, 2020. Its first flight is scheduled for late this year or early 2022.

Lessons learned from the XB-1 will be applied to the design and development of the 55-68 seat Overture. But there are only three years between the XB-1’s first flight and completing the first Overture prototype in 2025, according to the latest schedule given by Boom. The first test flight should happen in 2026, with certification and entry into service with United planned for 2029.

This is an optimistic roadmap, given that Boom still has to confirm the final design of Overture. It is collaborating with Rolls-Royce on “developing a custom propulsion system”, likely to be based on an existing engine architecture. This could be at a more advanced stage than has been communicated by both companies.

Boom XB-1

The Boom XB-1 demonstrator was rolled out in October but will start test flying only
later this year or early 2022. (Boom Supersonic)

Certifying a new supersonic transport is unknown territory for the regulators. While some lessons from may be applied, Overture is a different animal. Concorde was met by huge resistance over (noise) pollution, as the history of its arrival to the US tells us. Fifty years on, in a world more sensitive to the environmental aspects of flying and hinder, a new SST will be met with even more opposition.

Boom promises the latest noise-reduction technologies that won’t change existing airport noise footprints while flying only at supersonic speeds over water, but this has all to be proven. Book your seats in advance in the courtroom. Expect a careful, hence slow, approach from regulators and policymakers, and 2029 looks most optimistic.

2 – Overture’s sustainability

Boom and United have stated claims that the Overture will fly on 100 percent sustainable aviation fuels (SAFs). Boom advertises the aircraft as being net-zero carbon from day one. Both will work together to accelerate the production of greater supplies of SAFs.

There is little doubt that the supplies of SAFs will increase as more and more players enter the market this coming decade. All big companies plus new, specialized producers have announced plans for new SAF plants. The big concern is that all is done at a much too slow pace to meet the target of being carbon-free in 2050, as United and many other airlines have stated.

Boom has been working with Prometheus Fuels since 2019 to develop low-carbon fuels for the XB-1, using new technology to convert carbon dioxide from the atmosphere (direct capture) into jet fuel. It claims this will be done by using green energy for the conversion process, but critics say that the supply of green energy will be insufficient to cater to all demands.

Boom Overture United

The Overture can only operate over water, which like restricts its potential. Still, Boom says it could connect to 500+ destinations. (Boom Supersonic)

United is already fully committed to sustainable fuels. For over a decade, it has invested in the development of SAFs with AltAir Fuels and Fulcrum Biofuels. In 2016, United became the first to regularly use SAF on scheduled flights but only at a 30-percent mix. In April, it was one of the initiators of the Eco-Skies Alliance with twelve other non-aerospace companies to purchase 3.4 million gallons of SAFs this year. In its sustainability roadmap, it says it will make a multimillion-dollar investment in a start-up to develop direct air capture technology.

How promising these initiatives are, the Overture will have to demonstrate that it indeed can be a carbon-neutral airliner on its own. Boom’s sustainability efforts include the option of carbon offsetting, but the Overture would fail on its sustainability targets if it would heavily depend on this strategy.

Key to its sustainability will be the engines and their emissions. And to what rules they are measured against. In a 2018 report that has been quoted frequently again in recent weeks, the International Council on Clean Transportation criticized the lack of environmental standards for supersonic transports in the FAA Reauthorization Bill.
Based on information available three years ago from SST start-ups, ICCT claimed that a supersonic passenger aircraft would produce five to seven times the levels of carbon dioxides compared to a subsonic airliner.  On the popular North Atlantic route, this would translate to 3.9 tons per passenger for an SST compared to 0.76 tons for a regular aircraft.

Specifically, SSTs with derivative engines would fail to meet existing targets for environmental airliners.

Boom Overture cabin

The Boom Overture can seat between 55-68 passengers in Business Class comfort. But at what price? (Boom Supersonic) 

3 – The Overture business case:

Without the option of flying supersonic over land, Overture will be limited to routes that connect over water. According to Boom, there are still over 500 potential routes available. Not much has changed since then. But whereas and Air France predominantly used their Concordes on the transatlantic routes (especially in the late days of its history), United Airlines has the option to operate the Boom from its East and West Coast hubs on a more diverse network. New York-London, Paris, or Frankfurt come within reach of Overture with is 4.250 nautical miles range. At Mach 1.7, flight times would be reduced by half compared to subsonic travel.

The question is: at what price? Boom’s Blake Scholl has stated in the past that a transatlantic ticket on an Overture would be in the same $2.000 range as a Business Class seat on a subsonic airliner. This was before the Covid-crisis. The jury is still out whether business travel will recover fully or will lose a major chunk of its demand. In most recent financial results webcasts, CEO were saying that they believe business travel will largely come back and they backed this up with positives signs of forward bookings.

Before an Overture has done some serious route-proving flights, it is difficult to judge its economics like trip costs and costs per seat. These will depend on many factors like the aircraft’s appetite for fuel and load factors. United will surely have done its sums right before it determines the ticket price, but expect these to be in the high-end of the Business Class market. That is if the actually commits to the firm order for fifteen aircraft plus 35 options because United said its order is conditional to meeting safety, operational, and sustainability requirements. If the Overture appeals to other airlines is still an open question.

4 – Boom’s financial position:

The United announcement is a huge boost for Boom Supersonic. Despite the conditions set out by the airline, it is the first real order for the Overture. Japan Airlines (JAL) only has a pre-order for twenty while Virgin Atlantic has options on ten aircraft. Including all firm orders and options, Boom says it has commitments for seventy aircraft.

But a fifteen aircraft deal is still a very modest base for a multibillion investment project that is only in a demonstrator phase. Boom says that on May 1, it had secured $270 million in project funding, including that from JAL and Virgin. The next step from demonstrator to airliner will require huge funding that has yet to be confirmed. Blake Scholl has been sounding out investors all over the world in recent years, but this hasn’t resulted in any publicly confirmed agreements.

The question is what we should conclude from Aerion Supersonic’s announcement on May 23 to fold the program for a 12-seat supersonic business jet: is this indeed a reality check for the SST market, as we asked ourselves? The Aerion AS-2 was an advanced industrial stage, having secured partnerships with major leading suppliers and stakeholders. But is had just twenty firm orders, although the US-airframer claimed to have a backlog of $11.2 billion. Aerion seems to have collapsed as it was unable to transform from the development to the production phase, with sales too low to justify the huge investments.

Boom could be at the same crossroads. A successful test flight program of the XB-1 is key to the future of the Overture. The announcement on Thursday could be seen as either a vote of confidence from a leading in the program, but many think it is just a pr-stunt.  Boom still has to tick too many boxes on its roadmap to the first commercial flight. 

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