Defense Contract Types: Cost-Plus, Fixed-Price, and Their Impact on Margins

Introduction

The type of contract under which a defense company operates is one of the most important determinants of its margin profile, earnings volatility, and risk characteristics. Two defense companies can have identical revenue, operate in the same sub-sector, and serve the same government customer, yet produce dramatically different financial outcomes based on whether their contracts are cost-plus or fixed-price. Boeing's accumulation of $4.9 billion in losses on fixed-price defense programs through 2024 (the largest ever for its defense unit) provides the most vivid illustration of how contract type determines financial outcomes.

For A&D investment bankers, understanding defense contract types is not optional. Contract type analysis directly affects revenue forecasting, margin modeling, risk assessment in due diligence, and the valuation multiples you apply. This article breaks down the major contract structures, explains the risk/reward trade-offs of each, and shows how bankers use contract mix analysis in practice.

Defense contracts exist on a spectrum from full government risk assumption (cost-plus) to full contractor risk assumption (firm-fixed-price), with several intermediate structures that share risk between the parties.

Cost-Plus Contract (Cost-Reimbursement)

A contract where the government reimburses the contractor for all allowable costs incurred during performance, plus a negotiated fee (profit margin). The fee structure varies: cost-plus-fixed-fee (CPFF) provides a fixed dollar fee regardless of actual costs, while cost-plus-incentive-fee (CPIF) adjusts the fee based on whether the contractor comes in above or below a target cost. Cost-plus contracts are used for R&D, prototype development, and other work where costs are difficult to estimate in advance. They carry low financial risk for the contractor but cap profit margins at regulated levels (typically 8-12% of costs).

Cost-plus contracts are the safer option for contractors. The government pays all allowable costs (labor, materials, overhead, G&A) plus a fee that provides the contractor's profit. Because the government bears the cost risk, profit margins are intentionally constrained. On cost-plus-fixed-fee (CPFF) contracts, the fee is set at contract award and does not change regardless of actual costs. On cost-plus-incentive-fee (CPIF) contracts, the fee adjusts based on performance, creating a modest incentive to control costs while still protecting the contractor from catastrophic losses.

Cost-plus contracts dominate early-stage program work: research and development, prototyping, and initial low-rate production where the technical uncertainty makes cost estimation unreliable. Roughly 40-50% of total defense spending flows through cost-type contracts, and companies with portfolios weighted toward R&D and early-stage programs (Northrop Grumman's B-21 development phase, for example) tend to have significant cost-plus exposure.

Fixed-price contracts shift risk dramatically to the contractor. Under a firm-fixed-price (FFP) contract, the contractor agrees to deliver a defined scope for a set price, regardless of what it actually costs to perform the work. If the contractor executes efficiently and comes in under the budgeted cost, it keeps the difference as additional profit. If costs exceed the contract price, the contractor absorbs the loss.

This structure creates both the potential for outsized margins and the potential for catastrophic losses. Well-executed fixed-price production programs (where the technology is mature and production is efficient) can generate 12-18% operating margins, well above the 8-12% fees on cost-plus work. But fixed-price development programs, where the technology is unproven and cost estimation is inherently uncertain, can produce devastating losses if engineering challenges, supply chain disruptions, or inflation push costs beyond what was budgeted.

Boeing's defense unit provides the clearest illustration of fixed-price contract risk in recent defense history. The company accumulated $4.9 billion in total losses on fixed-price defense programs in 2024 alone, across several troubled programs.

The KC-46 tanker program has produced over $7 billion in cumulative cost overruns. Boeing signed a fixed-price contract to develop and produce the aircraft, but technical challenges (the remote vision system, boom deployment issues), supply chain complications, and inflation pushed actual costs far beyond the contract price. Under fixed-price terms, Boeing is responsible for all costs above the contract ceiling, creating billions in losses that the company cannot recover.

The MQ-25 Stingray unmanned refueling drone and the new Air Force One (VC-25B) program have produced additional billions in losses under the same fixed-price dynamics: development complexity exceeded initial estimates, and the contract structure left Boeing absorbing the cost growth.

Notably, Boeing did not book any charges on its fixed-price defense contracts in the first half of 2025, marking the first time since 2019 that the defense unit went two consecutive quarters without a loss. This improvement suggests the worst may be passing for Boeing's troubled programs, but the episode has permanently changed how the industry and its investors evaluate fixed-price contract risk.

Defense contract mix analysis is a core component of A&D due diligence and valuation work.

Margin forecasting. When building a financial model for a defense company, bankers project margins separately for cost-plus and fixed-price contract portfolios. Cost-plus margins are modeled as stable and predictable. Fixed-price production margins can be modeled with modest improvement over time as production efficiencies are achieved. Fixed-price development margins should be stress-tested with downside scenarios that assume cost overruns.

Valuation impact. Companies with higher proportions of fixed-price production work (where the technology is mature and execution risk is manageable) tend to earn higher margins and command higher multiples than companies weighted toward cost-plus R&D. However, companies with significant fixed-price development exposure may warrant a valuation discount for the execution risk Boeing's experience demonstrated.

Risk assessment in due diligence. On buy-side mandates, bankers scrutinize the contract mix to assess margin sustainability and identify potential risk concentrations. Key questions include: What percentage of revenue is fixed-price development versus production? Are there any programs with known cost overruns not yet fully reflected in financials? How does the contract mix trend as programs mature from development into production?