I agree this is a matter of breathing technique. My comments regarding the diaphragm (musculomembrane separating the abdominal and thoracic cavities of the body. Major inspiratory muscle) - most people have heard the word "diaphragm" if they are interested in singing, but many are unclear about what that means - learning to engage the muscles that create space for your lungs to fully expand is part of the technique of breath support (diaphragmatic breathing). There are also lower ribs that move out farther to create more capacity for air if you learn how to move them (intercostal breathing). Get thee to a good flute teacher! I had heard the term "diaphragm" regarding singing since I was in grade school, but had no one really explain breathe support until I took private singing lessons. There are alot of muscles involved with breath support. Being in good physical shape makes it easier to use them. Here is a page that discusses breathing technique for speaking. There are other links in the threads on singing (see the mega-thread I put together regarding that).
Projection, filling your audience with sound.

I am sure there is more regarding flute and breath support technique if you do a search on the net.

Alice