An injured mountain biker has been flown to Wellington Hospital in a serious condition after a crash near Upper Hutt.

The Westpac rescue helicopter, with a Wellington Free Ambulance paramedic on board, was called to the scene on a track above Maidstone Park, Upper Hutt, at 1.25pm.

A 56-year-old Silverstream man was treated for a spinal injury and was now in stable condition.

Westpac rescue helicopter crewman Dave Greenberg said the man was travelling along a track and did not see an upcoming jump. "He said his front wheel fell away and he was thrown over his handlebars, landing on his head."

The man was wearing a helmet.