I want to know the answer to the following question:
What became the main source of Bermuda's economy in the 1970's?
All the background I'm provided with is that "In 1948, regularly scheduled commercial airline service by land-based aeroplanes began to Kindley Field (now L.F. Wade International Airport), helping tourism to reach its peak in the 1960s–1970s.". Is that enough to answer the question?
Answer: no