Leeham News and Analysis
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Bjorn’s Corner: Faster aircraft development. Part 22. Serial Production.
By Bjorn Fehrm and Henry Tam.
January 9, 2026, ©. Leeham News: We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.
The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.
We will use the Gantt plan in Figure 1 as a base for our discussions. We have completed flight testing of the flight test aircraft and obtained a design Type Certificate (TC). We now examine the production preparations and the serial production phase.
Figure 1. A generic new Part 25 airliner development plan. Source: Leeham Co. Click to see better.
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The state of alternative propulsion aircraft? Part 4.
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By Bjorn Fehrm
December 4, 2025, © Leeham News: In our series about alternative propulsion aircraft, last week we looked at the aircraft batteries. These are heavy components with very low energy capacity per unit weight.
To illustrate the kind of aircraft-level challenges the batteries pose, we are using our Aircraft Performance and Cost Model (APCM) to design a typical alternative-propulsion battery-electric aircraft and then fly it on typical missions.
The aircraft is similar in size to a 9-seat Tecnam P2012 commuter (Figure 1) but optimised for Battery-Electric propulsion.
Figure 1. The Tecnam P2012 nine-seater commuter. Source: Tecnam.
The APCM will give us the airframe-level energy consumption for each phase of the flight. Subsequently, we can add the different losses in the propulsion system to determine the energy consumed from the battery and the endurance/range it offers, dependent on VFR or IFR mission reserves.
Bjorn’s Corner: Faster aircraft development. Part 18. Prototype Parts and Systems.
By Bjorn Fehrm and Henry Tam.
November 28, 2025, ©. Leeham News: We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.
The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.
We will use the Gantt plan in Figure 1 as a base for our discussions. We have exited the Detailed Design phase after conducting Critical Design Reviews, CDRs, and now enter into Prototype Manufacturing.
Figure 1. A generic new Part 25 airliner development plan. Source: Leeham Co. Click to see better.
** Special thanks to Ron Everlove for helping with this article **
The state of alternative propulsion aircraft? Part 3.
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By Bjorn Fehrm
November 27, 2025, © Leeham News: In our series about alternative propulsion aircraft, last week we looked at the electric motor of an electric aircraft, which drives propellers or fans. It’s a component that is straightforward to develop, but the certification requirements for the aircraft and VTOL industry have slowed progress.
Now we look at the component that causes trouble for all alternative propulsion aircraft, except those that burn hydrogen in gas turbine engines: the batteries. Batteries work well in cars, where the requirement for energy capacity relative to weight is much lower and where energy recovery during braking reduces the energy required from the battery.
Figure 1. The battery-electric aircraft that flies operational trials as we speak, the Beta Technologies Alia CX300. Source: Leeham Co.
Aircraft batteries are a heavy component with very low energy storage capacity. Today’s aircraft battery system has about 60 times lower energy density per kg or lb than aircraft fuel.
The hope over the last decade has been that this relationship should improve. It has, it’s gone from about 70 times to 60 times in the last 10 years. This will improve further, the question is if it will continue at the slow pace of the last 10 years or not?
Bjorn’s Corner: Faster aircraft development. Part 17. Critical Design Review, CDR.
By Bjorn Fehrm and Henry Tam
November 21, 2025, ©. Leeham News: We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.
The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.
We will use the Gantt plan in Figure 1 as a base for our discussions. We are in the Detailed Design phase, and it’s time to conduct the Critical Design Reviews, CDRs.
Figure 1. A generic new Part 25 airliner development plan. Observe the CDRs. Source: Leeham Co. Click to see better.
The state of alternative propulsion aircraft? Part 2.
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By Bjorn Fehrm
November 20, 2025, © Leeham News: In our series about alternative propulsion aircraft, we started last week by discussing what happened after the trigger by the Airbus E-fan flight in 2014 and the introduction of the Tesla Model S car two years before. The alternative propulsion aircraft projects that followed had a rocky path. They followed the Gartner Hype-curve, Figure 1.
There were hundreds of projects announced, more or less serious. A few of these came to producing hardware, and flew test flights, then stopped. Most stayed as PowerPoint presentations and fancy renderings, promising capabilities that were not possible to realize. The result was that we passed the Peak of Inflated Expectations and entered the Trough of Disillusionment. Investors fled to AI, and projects froze or stopped.
Figure 1. The Gartner Hype-curve. Source: Gartner Inc.
By 2025, we are in the Disillusionment phase. As there are signs we can now enter a phase of real, sustainable progress, it’s timely to take stock of where we are and what progress we can expect over the next decade.
To understand why progress has been so difficult, after explaining that learnings from Cars are not transferable last week, we start by focusing on two components that we find in every alternative propulsion concept, the Electric Motor and the Battery system. Of the two components, the motor is the most straightforward to develop and certify for an aircraft. Still, we have only limited progress so far, and we detail why in today’s article.
The Battery System is the most challenging component for alternative propulsion aircraft, both in development and in use. We will spend next week’s article detailing why and how it has slowed down progress so far, and how this can change going forward.
Bjorn’s Corner: Faster aircraft development. Part 16. Certification Compliance Planning.
By Bjorn Fehrm and Henry Tam
November 14, 2025, ©. Leeham News: We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.
The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.
We will use the Gantt plan in Figure 1 as a base for our discussions. We are in the Detailed Design phase and working with the Certification Compliance plan.
Figure 1. A generic new Part 25 airliner development plan. Source: Leeham Co. Click to see better.
*** Special thanks to Andrew Telesca for helping with this article ***
Bjorn’s Corner: Faster aircraft development. Part 15. Detailed Design of Structures
By Bjorn Fehrm and Henry Tam
November 7, 2025, ©. Leeham News: We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.
The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.
We will use the Gantt plan in Figure 1 as a base for our discussions. We have now entered the Detailed Design phase, where we use the Airframe structure design as an example of the work during this phase.
Figure 1. A generic new Part 25 airliner development plan. Source: Leeham Co. Click to see better.
*** Special thanks to Paul Smith for helping with this article ***
Bjorn’s Corner: Faster aircraft development. Part 13. Preliminary Design Review, PDR.
By Bjorn Fehrm and Henry Tam
October 24, 2025, ©. Leeham News: We do a series about ideas on how the long development times for large airliners can be shortened. New projects talk about cutting development time and reaching certification and production faster than previous projects.
The series will discuss the typical development cycles for an FAA Part 25 aircraft, called a transport category aircraft, and what different ideas there are to reduce the development times.
We will use the Gantt plan in Figure 1 as a base for our discussions. Today’s topic, the Preliminary Design Reviews, PDRs, are marked in the chart.
Figure 1. A generic new Part 25 airliner development plan with PDR marked in time. Source: Leeham Co. Click to see better.