The Guernsey and Alderney lifeboats as well as two helicopters are combing an area north of Alderney for the Piper Malibu plane.
Air Traffic Control have confirmed the aircraft was travelling from Nantes in Western France to Cardiff when it went missing.
In a statement Guernsey Police said: “A search and rescue operation is currently underway off the north of Alderney
after a light aircraft disappeared from radar several hours ago.
“Two helicopters alongside the Guernsey and Alderney lifeboats are searching for it.”
It is not known how many people were on board the single-engine Piper Malibu, but it normally carries one pilot and up to five passengers.