Why is titanium known as a strategic metal?

Titanium is known as a strategic metal because it is essential for the country's economy and defence. For example:  It  is used for alloys with with aluminium, molybdenum, manganese, iron, and other metals. These alloys of titanium are used principally in the aerospace industry, for both airframes and engines, where lightweight strength and ability to withstand extremes of temperature are important.