Premier League footballer Emiliano Sala was on a light aircraft which went missing over the Channel Islands.
The £15m Argentine striker, 28, was one of two people on board the Piper Malibu which lost contact off Alderney in the Channel Islands on Monday night.
Cardiff City, which signed Sala from French club Nantes in a record deal on Saturday, said it was “very shocked”.
Guernsey Police said there was “no trace” of the Cardiff-bound flight and his family said they felt “desperate”.
Sala’s father, Horacio, told Argentine TV channel C5N, he heard the news from a friend.
“I didn’t know anything. I couldn’t believe it,” he said. “I’m desperate. I hope everything goes well.”
Meanwhile, John Fitzgerald, chief officer of the Channel Islands Air Search, said the probability of finding anyone alive from the missing aircraft was “reducing very rapidly”.
“I think with the sea temperatures and the sea conditions the chances of finding anybody alive are reducing all the time,” he said.
“The sea temperatures are very, very cold and just sap the core temperature of anybody in the water very, very quickly.”
The plane left Nantes in north west France at 19:15 and had been flying at 5,000ft when it contacted Jersey air traffic control requesting descent, Guernsey Police said.
The plane lost contact while at 2,300ft and disappeared off radar near the Casquets lighthouse, infamous among mariners as the site of many shipwrecks, eight miles (13km) north-west of Alderney.
The force added UK authorities have been calling airfields on the south coast to see if it landed there but there had been no confirmations and a decision about an overnight search would be made at sunset.
A spokesman for the French Civil Aviation Authority said the Piper PA 46 Malibu aircraft was French but had not been registered in France.
“We can confirm Emiliano Sala was on board,” he said.
“This morning, the French research started with one French national navy ship and one aircraft. The investigation will determined which authority will take the lead on the research.”
Sightings of red flares were reported during a lifeboat and helicopter search, but “nothing of significance was found”, a Channel Islands Air Search spokeswoman said.
Police said on Tuesday more than 100sq miles had been searched by five aircraft and two lifeboats. The search had resumed after being called off overnight “due to strengthening winds, worsening sea conditions and reducing visibility”.
Cardiff Airport confirmed the aircraft was due to arrive from Nantes but a spokeswoman said there were no further details.
Guernsey harbour master Captain David Barker said no distress call had been received and if the search continues into the night it is unlikely to have a good outcome.
“It’s far easier to see something on the surface in daylight,” he said. “We are looking for any traces of an aircraft, a life raft, persons in the water, life jackets.”
The Met Office said conditions were not “too intense” at the time the aircraft went missing but had become wetter and windier later in the evening.
John Fernandez, a reporter for BBC Guernsey, said it was a difficult area to search.
“A number of search vessels are out searching the area. It’s known for its strong currents – there are a number of shipwrecks,” he added.
“The search area is absolutely massive at the moment. They’re searching a number of different spots at the moment – they’re not sure whereabouts this plane might have gone down.”