Never lie to US immigration!
Renting a plane in the US is not considered much different to renting a car. The question is extremely unlikely to come up, but if it does, answer truthfully - you are doing some touring and renting a plane to do it. Believe it or not, in the US, that's perfectly legal!
PS that didn't quite answer your question. I don't specifically mention flying and have never been asked about it in 50+ visits despite always having headset etc in my bag.