Tangy frozen yogurt behemoth Pinkberry is planning to open a fourth Boston area store in Terminal C of Logan Airport. Boston.com's travel column Pack Up says that the store will be one of thirteen new retailers coming to this terminal alone, including another Legal Sea Foods, which are opening one by one in 12,000 square feet of space made available by renovations. Pinkberry also has locations in Harvard Square, on Newbury Street and at the Pru. Weary fro-yo loving travelers will surely rejoice at coming back to Boston and being greeted by billions of friendly lactobacillus bulgaricus and streptococcus thermophilus. In other Logan news, Potbelly Sandwich Shop didn't quite make its planned March opening but is still on its way.