After a second full day of searches, rescuers suggested there was “no hope” of finding the missing pair. John Fitzgerald, Chief officer of Channel Islands Air Search, said “even the most fit person” would only last a few hours in the water.
The plane lost contact while at 2,300ft (700m) and disappeared off radar near the Casquets lighthouse, infamous among mariners as the site of many shipwrecks, eight miles (13km) north-west of Alderney.
Mr Fitzgerald said: “Sadly, I really don’t think, personally, there is any hope. At this time of year the conditions out there are pretty horrendous if you are actually in the water.”
The aircraft, which was built in 1984, is registered in the United States rather than Britain through a company based in Norfolk. The firm, Southern Aircraft Consultancy, charges owners around £500 per year to register their aircraft with the Federal Aviation Authority, which means it is harder for the owners to be identified.
Guernsey police announced the search was being suspended shortly after 5pm. “After an intensive search using multiple aircraft and one lifeboat over the last nine hours, we have found no trace of the missing plane,” the force said in a statement. A decision about whether to recommence the search operation will be taken early on Thursday.