Prof. P.C. Mahalanobis is recognized as the architect of Indian planning due to his pivotal role in shaping India's economic development and planning. Here's the reason for his recognition:

1. Role in Economic Planning: P.C. Mahalanobis was a renowned Indian statistician and economist. He played a crucial role in the formulation and implementation of India's Second Five-Year Plan (1956-1961) and the subsequent plans. His contributions were instrumental in shaping the economic planning and development strategies of post-independence India.

2. Use of Statistical Methods: Mahalanobis emphasized the importance of using statistical methods and quantitative techniques in economic planning. He advocated for the application of statistical data and analysis to make informed decisions and allocate resources efficiently. This approach helped in rationalizing economic policies and resource allocation.

3. Industrialization and Growth: Mahalanobis' approach to planning focused on rapid industrialization and the development of heavy industries. His model aimed at reducing dependence on imports and promoting self-sufficiency in key sectors of the economy. This approach contributed to India's industrial and economic growth.

4. Influence on Planning Commission: P.C. Mahalanobis served as a member of the Planning Commission of India and was influential in guiding the country's economic development policies. His emphasis on quantitative planning and the role of the public sector in industrialization left a lasting impact on India's planning process.

Overall, P.C. Mahalanobis is recognized as the architect of Indian planning because of his significant contributions to economic planning and his role in shaping India's development strategies, particularly during the early years of post-independence economic planning.