What is the most profitable part of the aviation industry to invest in

What is the most profitable part of the aviation industry to invest in? Airlines themselves are capital intensive, very competitive, and companies are lucky to profit. Next in the value chain are airplane manufacturers like Boeing and Airbus who make the frames, but once they sell, there is not much value after that. If you move along the chain to the engine manufacturers, such as Rolls Royce (LON:RR) - that is where the heat is. Once sold, constant servicing is required. Its order book is further boosted by fuel efficiency upgrades required across the industry. It shares a duopoly (with GE) in the wide body jet market. Its strong position in a robust industry has seen its shares up 190% over five years. We discuss Rolls, the broader macro environment, Healthcare sector, and Oil sector in the following short video: (VIEW LINK)