See our slideshow of the Guide to Hidden Airline Fees. Planning to attend your annual family reunion in Chicago , you spend hours searching online for the best available plane fare. Finally, success: on a discount-booking site you find a round-trip ticket on US Airways for less than $180. Done deal. At the airport, though, you discover that checking your two suitcases (one heavy with presents for family members) will set you back $50. Then, on the plane, a flight attendant informs you that a …