Sample Revised Thesis

I started with:

The airplane had a major affect on America.

• what part of American society or culture was affected? Warfare? Travel?

Ok. How about:

Air travel is really important in America.

• better-we are dealing with air travel. Why is it important?
• what time period or focus is appropriate?

Try again. Now I've done some research and realized that airlines were deregulated in 1978. This meant that the U.S. government no longer had control over airline fares and also streamlined the process required to start a new airline. After the airlines were deregulated there was more competition in the marketplace which resulted in lower airfares. A downside: the increased competition resulted in the failure of a half-dozen major American airlines.

I'll go with:

The 1978 Airline Deregulation Act benefited the air traveler in America by providing more options and lower airfares.