More and more people are looking for more sustainable and less polluting ways of getting around. They could be represented by Greta Thumberg who is travelling to the climate summit from the US by boat to Lisbon.

A new technology emerges that allows a reduction in the emission of polluting gases. 

The economic boom leads people to travel more and airlines need to buy more aircrafts to expand the fleet or replace older ones. 

There is a US regulation that requires companies to be certified. 

Interest rates will influence the cost of investment projects for which external financing is needed.

The new generations are not studying engineering studies, which are the most appropriate for the company's needs.

Governments may favour the establishment of certain industries. For example, government support for the aerospace and aeronautics industry in general or the military.