Impatient, grumbling and stuck: That's the winning combination for airport marketing. Those bins that hold your shoes at the airport are actually called divesting trays and Security Point Media is betting that advertisers will divest themselves of lots of money to get their ads in them. It could be a dream come true - to reach a captive (albeit possibly grumpy) audience of millions. The SecureTray System, which includes tables, bins and carts for transporting them, was granted a yearlong pilot program by the TSA last year, spanning 14 airports and ending in May. Online footwear retailer zappos.com pointed fliers to its Web site with quips like "Great Shoes. No Line."The future of the medium hangs in the balance while the TSA deliberates over whether to approve the program for airports nationwide. A favorable decision is likely since getting free equipment could potentially save the agency millions - each tray costs $7 and must be replaced every three months. TSA approval does not guarantee that every airport will decide to accept checkpoint ads, though they would receive a share of revenue. Hot spots like LAX, which sees 70 million travelers each year, are prepared for takeoff and plan to use the SecureTrays to place ads of their own.