Image caption Richard Bach is in a serious condition

The US author of 1970s short novel Jonathan Livingston Seagull has been seriously injured in a plane crash.

Richard Bach was reportedly trying to land his small plane on San Juan island in Washington state when he hit power lines and got trapped in the cockpit.

Local media reported that a group of holidaymakers had to cut him free.

His son, James, said his father was flying alone and suffered a head injury and broken shoulder. Bach, 76, is known to be a keen aviator.

"Right now we're waiting for the sedation to wear off, for him to fully wake up," James Bach told the Associated Press news agency.

Jonathan Livingston Seagull, published in 1970, is a fable telling the story of a bird that is guided through spiritual lessons.

The book, a bestseller made into a film in 1973, gave Bach a loyal following.