3 Sheets To The Wind's advice is generally applicable, for DOMESTIC FLIGHTS. In major international airports there ARE drug dogs in the international terminals. I even saw 4 (!!!) dogs with officers walking around outside the indianapolis airport last time I was there (which is not even a major airport).

My advice, don't do it. Airport security is more strict than ever, especially in the US for international flights. America hates pot a lot more than london, they ain't gonna be happy if they catch you carrying any cannabis.