By http://www.aeroinside.com/item/4276/austrian-b763-near-toronto-on-jun-18th-2014-white-smoke-in-cockpit

An Austrian Airlines Boeing 767-300, registration OE-LAZ performing flight OS-66 from Chicago O’Hare,IL (USA) to Vienna (Austria) with 195 people on board, was enroute at FL330 about 130nm northeast of Toronto,ON (Canada) when the crew noticed white smoke in the cockpit, which dissipated after about 15 seconds, the odour however remained. The crew worked the related checklists and decided to turn around and divert to Toronto. On downwind to runway 05 the crew requested emergency services on stand by due to an overweight landing and a necessary brakes inspection. The aircraft landed safely on runway 05 about 35 minutes after turning around and taxied to the apron with emergency services in trail. The Canadian TSB reported that the crew used autobrakes 1, the brakes temperatures did not exceed 270 degrees C. Maintenance was subsequently advised that a ground unit used in Chicago, that supplied pneumatic pressure to the aircraft due to the non-availability of the APU, had broken down and possibly contaminated the pneumatic ducting. The pneumatic ducting was cleaned, the system was operated using engine power until the odour had disappeared, then the aircraft was returned to service. The remainder of the flight was cancelled, the passengers were rebooked onto other flights. The occurrence aircraft resumed service 22 hours after landing as flight OS-72 from Toronto to Vienna.