I may be the exception, but I've got several ball caps I wear when flying and some of them are pretty filthy from years of use. My wife refuses to let me out of the house with them if I'm headed anywhere but the airport. I tried washing one in the washing machine, but the bill got badly deformed and even I wouldn't wear it any more. Then my wife got me this thingamajig for Christmas that let's me wash my ball caps in the dishwasher. I tried it on my nastiest Maule cap and it came our pristine and the bill is still properly shaped. It was the best weird little gift I've received in ages:
http://www.amazon.com/Ball-Cap-Buddy-199-851414000038-LTC-1-Ballcap/dp/B0013FGVW2/ref=sr_1_1?ie=UTF8&qid=1419640472&sr=8-1&keywords=baseball+hat+washer





