Hochtief AG's airport-operating unit has five bidders left in the running and offers are valued at about 1.5 billion euros ($2.2 billion), Platow Brief reported, without saying how it got the information.The bidders are Vinci SA, Fraport AG in cooperation with Deutsche Bank AG's RREEF division, Allianz SE (the insurance company) together with Global Infrastructure Partners (GIP), as well as the operators of the Shanghai and Singapore Changi airports (Changi Airport Group),according to Platow. Binding offers are expected within three weeks, the publication said.