Increasing commonality across their models allows commercial aircraft manufacturers to reduce the product development cycle time and tailor their models to their customers' needs. The cockpit is an area where commonality is thought to be particularly desirable, since it also simplifies the pilots training process for the airline companies. However, no set of metrics is currently able to measure the efficiency of commonality application at this level from a total lifecycle standpoint. In this paper, a set of metrics is proposed adapted to large commercial aircraft and taking into account the main parts of the product lifecycle. The concept of lead time is central in the measurement of commonality, as it strongly influences the value of the aircraft for all primary stakeholders. The extent has been examined to which these metrics are independent from aircraft particularities (such as physical dimensions). Indicated are their limitations and what additional research should be performed to obtain a set of metrics able to measure the efficiency of commonality implementation for the whole aircraft. The example of two competing medium-haul aircraft families is used to test the set of metrics. The efficiency of commonality according to the metrics has been evaluated and we compared with field results obtained from the manufacturers' studies and from the results of interviews of airlines pilots. It has been shown how the set of metrics can help determining how to optimize the level of commonality for all stakeholders. This paper has presented a set of metrics to measure the quality of commonality implementation in the cockpit of commercial aircraft. Commonality is considered here in abstraction from the technical properties of the products studied. It is divided into three constructs: standardization, reusability and modularity. Each of these constructs is measured from the manufacturer and from the customer points of view. A total of eleven metrics is necessary to fully comprehend the cockpit commonality efficiency. Further analysis discusses the application of this set of metrics to the entire aircraft as well as to other types of aerospace vehicles. A parallel is drawn with the automotive industry, and further research in that domain could lead to a better understanding of the applicability of commonality metrics to other types of engineered products. A case study tests this set of metrics by comparing two competing medium-haul aircraft families: the derivatives of the A320 and those of the 737-300.