You might succeed in carrying it on board from the UK to the USA (depending on which airline your traveling with). However, you might run into some difficulties coming back with the TSA - these are the folks who do airport security in the US - and if your luggage doesn't fit the gauge of the security scanning machine (and a Hiscox case doesn't) they'll send you back to check it in. On a reassuring note, in my experience of carrying my Avalon in a Hiscox and having to check it in, so far so good. Make sure you cover it in FRAGILE stickers - it may not mean anything to the luggage handlers but my philosophy is that if they do trash it, they'll be more embarrassed and the negative publicity value could be something they'd rather avoid. And of course, insure your guitar!