An Alaska Airlines Airbus A320-200, performing flight from Seattle to Santa Ana (USA), reported unusual odour on board.

• Aircraft was climbing through FL270 out of Seattle when the crew stopped the climb and decided to return to Seattle reporting an unusual odour on board.
• The aircraft landed safely back in Seattle about 30 minutes after departure.
• Three cabin crew were taken to a hospital for a precautionary medical checkup.
• Emergency services did not detect any odours on entering the aircraft after landing. The airline reported the cause of the odour is being investigated.