No travelers like airline fees, but some of them are more aggravating than others. My least favorite is ANY fee where you have to opt-out, i.e. un-check a box not to pay it. United Airlines is trying to sell you extra miles with each trip. When checking in online (and at airport kiosks), this is an opt-out offer.

Openskies offers money back guarantee, Thai plane searched after bomb scare, ILFC scolds Boeing and Airbus