FRANKFURT  - Frankfurt airport, Europe’s third busiest hub, braced for travel chaos Thursday, with as many as half of all flights cancelled due to a strike by airport tarmac workers over pay. Fraport, the company which owns and operates Germany’s largest airport, is aiming to keep “50 percent of operations up and running” on Thursday and Friday despite a walkout by so-called “apron control” staff, who direct aircraft in and out of their parking positions, a spokesman told AFP. It was primarily up to the airlines themselves to decide which flights would take off or land, said spokesman Mike Schweitzer, advising passengers to contact the airlines directly.