For aerospace and defense programs, scale rarely arrives all at once. Programs grow one supplier, subsystem, and software release at a time. Teams add another product variant. A new verification activity appears after a design review.
Before long, a program that once felt manageable evolves into a highly interconnected system with millions of relationships between requirements, designs, software, tests, risks, and compliance evidence.
At first, none of these changes feel drastic, then engineering teams suddenly find themselves spending more time coordinating work than completing it. Reviews take longer and traceability becomes harder to maintain. Certification preparation becomes a weeks-long event.
At this point, complexity grows faster than the program itself. As complexity grows, so does the effort required to keep the program aligned.
This is the hidden cost of scale, and the challenge that many long-running aerospace and defense programs face.
The Real Challenge of Engineering Scalability
When organizations talk about engineering scalability, conversations often focus on technical specifications. How many users can the system support? How many requirements can it store?
Those questions matter, but they miss the larger issue. For engineering organizations, scale is more about operational complexity. A program has reached scale when engineers spend more effort coordinating work than advancing it.
That coordination takes many forms:
- Keeping aircraft, system, subsystem, hardware, and software requirements aligned as designs evolve
- Synchronizing requirements exchanged with suppliers and subcontractors
- Managing baselines across variants, increments, and modernization efforts
- Maintaining traceability from regulations and safety objectives through requirements and verification evidence
- Assessing downstream impacts before approving a change
- Coordinating formal reviews across engineering, safety, quality, certification, and program stakeholders
- Maintaining verification coverage as software releases continue throughout the program
Every additional relationship between engineering artifacts increases the amount of coordination required to keep the program moving, and makes managing dependencies more challenging.
Complexity Creates Hidden Costs Long Before Systems Reach Their Limits
Many long-running aerospace and defense programs don’t experience a single moment when a tool suddenly stops working. Instead, small inefficiencies accumulate until they become significant program costs.
Coordination Replaces Engineering
As programs mature, engineers often spend more time confirming decisions and validating assumptions than solving technical problems.
Questions that once took minutes now require conversations across multiple teams.
- Has this requirement already changed?
- Which baseline is current?
- Has verification been updated?
- Who approved this design?
None of these activities create customer value, yet they consume an increasing percentage of engineering time.
Work Becomes Fragmented
When systems struggle to support growing programs, teams naturally create workarounds. For example, separate projects are established for different product variants. Each workaround solves a local problem, but collectively they introduce organizational risk. Instead of one product definition, teams begin maintaining multiple versions.
This runs counter to the direction of modern digital engineering. DoD Instruction 5000.97 establishes digital engineering as policy for the development and sustainment of defense systems, while current DoD guidance emphasizes interoperability, information sharing, and collaboration across the lifecycle.
Change Becomes More Expensive
Long-running programs are exposed to change from multiple directions. Supplier disruptions, software-development delays, design changes, evolving mission needs, and verification findings can all alter the product definition over time.
GAO has identified supplier, software, and quality issues among the factors contributing to delays across major defense acquisition programs.
At the same time, missions evolve and software continues developing long after hardware decisions have been made. The challenge for teams here is understanding the full consequences of these changes.
A single requirement modification may affect dozens of downstream requirements, verification activities, interface definitions, software components, and test cases. When those relationships aren’t immediately visible, engineering teams spend valuable time discovering impacts.
Verification also becomes more interconnected as programs mature. A software requirement may eventually trace to software-in-the-loop testing, hardware-in-the-loop testing, integration results, and other verification evidence. When the requirement changes, teams need to know which evidence must be reviewed or rerun rather than discovering the impact later.
Long Timelines Give Complexity Time to Compound
Aerospace and defense programs already operate across long development lifecycles, giving engineering complexity years to accumulate. When schedules extend beyond the original plan, teams must manage that complexity even longer.
The U.S. Government Accountability Office (GAO) found in its 2024 Weapon Systems Annual Assessment that major defense acquisition programs that had delivered an initial capability took an average of 11 years to do so, three years longer than originally planned.
That timeline has continued to grow. In its 2026 Weapon Systems Annual Assessment, the GAO reported that the average time for major defense acquisition programs to deliver a capability had increased to more than 12 years. Across 104 of the Department of Defense’s costliest weapon programs, planned investment exceeds $2.4 trillion.
Every additional year can mean more requirements changes, supplier inputs, software releases, baselines, verification activities, and engineering decisions that teams must keep aligned. What begins as a small coordination problem early in development can become a significant source of cost and delay when repeated across a program lifecycle measured in years.
Compliance Evidence Grows With the System
For safety-critical airborne systems, engineering scale also means compliance scale. Teams may need to maintain alignment with system-level development and safety processes under ARP4754A and ARP4761A, software development assurance under DO-178C, airborne electronic hardware assurance under DO-254, and applicable FAA airworthiness requirements such as 14 CFR Part 25. The FAA recognizes DO-178C, DO-254, and aspects of ARP4754A among the industry standards and recommended practices used for development assurance of complex and integrated aircraft systems.
Each framework introduces evidence that must remain connected to the evolving product definition. A change to an aircraft-level requirement can affect system requirements, software or hardware requirements, safety analyses, verification activities, test results, and ultimately the evidence used to demonstrate compliance.
The challenge grows in two ways. Teams are managing more engineering artifacts while also maintaining the relationships that explain why those artifacts exist, what they satisfy, and how they were verified.
Review Debt Adds Up
Engineering organizations often think about technical debt, but not many discuss review debt.
As programs expand, formal review cycles become more difficult to execute. A requirement review that once involved a small systems team may eventually require input from software, hardware, safety, verification, certification, suppliers, and program leadership. More participants, more affected artifacts, and more decisions requiring approval can turn reviews into schedule constraints.
Eventually, reviews stop functioning as engineering checkpoints and become schedule constraints. For certification-bound programs, that creates additional risk.
Formal reviews provide evidence that engineering decisions were evaluated, approved, and understood before development moved forward. As programs scale, maintaining that discipline becomes increasingly important.
Certification Debt Is Even More Expensive
Some engineering debt remains hidden until the end of a program, but certification debt behaves differently. It accumulates throughout development before appearing during customer reviews, qualification activities, or regulatory audits.
Teams may discover missing rationale, incomplete traceability, or disconnected evidence. Each missing connection represents engineering work that eventually must be reconstructed.
Consider the traceability required for aircraft certification. A regulation under 14 CFR Part 25 may need to be decomposed into individual provisions, connected to aircraft-level requirements, and ultimately supported by downstream system requirements and verification evidence. As the number of requirements, variants, and changes grows, maintaining that chain manually becomes increasingly difficult.
One missing relationship may seem small in isolation. Across thousands of requirements and years of development, those gaps become certification debt that teams eventually have to investigate and reconstruct.
Program Knowledge Has to Outlast the Team
Time creates another scaling challenge: the people working on the program change. Long-running programs also have to survive personnel change. Engineers, program managers, suppliers, and reviewers rotate throughout development, while the rationale behind engineering decisions must remain understandable years later.
When that context lives primarily in meetings, email, spreadsheets, or individual memory, turnover creates another form of scale debt. New contributors have to reconstruct why a requirement exists, which alternatives were considered, what was approved, and what downstream work depends on that decision.
At scale, preserving engineering rationale becomes as important as preserving the requirement itself.
Sustainable Speed Depends on Managing Relationships
Modern aerospace and defense programs are becoming more software-intensive, multidisciplinary, and iterative. The Department of Defense’s 2025 Acquisition Transformation Strategy reflects that shift, calling for broader adoption of digital and model-based engineering to support rapid, iterative design and technology insertion.
Those approaches can increase engineering velocity, but they also increase the volume of relationships that programs must manage.
More frequent software releases create additional verification cycles. Product variants create additional baselines. Digital models create more interconnected engineering data. AI-assisted development can create and modify engineering artifacts faster than traditional workflows.
As engineering teams move faster, they also create more relationships and downstream impacts that must remain connected throughout development, and long after programs have grown beyond their original scope. To pull that off requires scalable engineering practices.
What Scalable Engineering Practices Have in Common
Supporting enterprise aerospace and defense programs requires scalable engineering practices that preserve visibility as requirements, reviews, verification, risks, and decisions continue evolving.
That means:
- Understanding downstream impacts before implementing change.
- Maintaining a trusted product definition across engineering disciplines.
- Supporting formal review processes throughout the lifecycle.
- Preserving traceability as products evolve.
- Giving AI-assisted workflows trusted, governed product context instead of disconnected information.
These capabilities help organizations sustain engineering speed as programs become more complex, rather than slowing under the weight of that complexity.
Build for Long-Term Complexity
Engineering scalability ultimately shows up in the decisions teams can continue making as a program grows.
- What changed and what does it affect?
- Which baseline is current?
- Has it been reviewed?
- Has it been verified?
- Can we prove it?
Those questions become harder to answer as programs add suppliers, variants, software releases, requirements, verification evidence, and years of development history.
When teams can continue answering them with confidence, complexity at scale becomes manageable instead of costly.
Continue Exploring
Learn how Live Traceability™ helps engineering organizations maintain visibility, assess change impacts, and reduce complexity as programs grow in our Guide to Requirements Traceability.
