Argentinean footballer Emiliano Sala was on board a light aircraft that disappeared en route to Cardiff for his English Premier League debut, France's civil aviation authority says.
Sala was flying from the French city of Nantes to the Welsh capital when the plane lost radar contact off the English Channel island of Guernsey late on Monday (UK time).
Rescue aircraft and boats had searched more than 1000 square miles (2600sq km) of sea for the single-engine Piper Malibu by noon on Tuesday, but "no trace of the missing aircraft had been found," Guernsey police said.
An official involved in the air search says no survivors are expected to be found.
"After all this time the weather's quite cold, the water is very cold out there ... I am not expecting anyone to be alive," Channel Islands Air Search chief officer John Fitzgerald told The Associated Press.
"I don't think the coastguard are either. We just don't know how it disappeared at the end of yesterday."
The 28-year-old Argentine-born forward joined struggling Cardiff City from FC Nantes last week for a club record fee of about 17 million euros ($NZ29 million). He had played in France since 2012.
"We expected Emiliano to arrive last night into Cardiff and today was due to be his first day with the team," club CEO Ken Choo said in a statement.
"We continue to pray for positive news."
Tuesday's training session was called off.
"The management and the whole club are staying hopeful and the whole FC Nantes family is praying for Emiliano Sala and the other passengers to be found safe and sound," Nantes said in a statement.
Sala's father Horacio told Argentine TV channel C5N: "I didn't know anything because I'm away from home, I'm a truck driver. A friend who saw it on TV told me. I'm in despair."
Julio Muller, the mayor of Progreso, the small town in the farming province of Santa Fe where Sala grew up, told Clarin online: "The town is in shock. The only thing we were talking about was his transfer."
France's football federation postponed Nantes' French Cup last-32 game against Entente Sannois-Saint Gratien that had been scheduled for Wednesday.
Sala on Monday tweeted a photo of himself bidding farewell to his Nantes team mates, saying. "The last one. Ciao FCNantes."