There is “genuine concern” Premier League footballer Emiliano Sala was on a flight which disappeared between France and Cardiff.
It is feared the Argentine striker was one of two people on board the Piper Malibu, which disappeared off Alderney on Monday night.
Cardiff City, which signed the 28-year-old from French club Nantes on Saturday, said it was “seeking clarification” as to what happened. A search is under way.
Cardiff Airport confirmed the aircraft was due to arrive from Nantes but a spokeswoman said there were no further details.
HM Coastguard said the disappearance was not in the UK search and rescue area, but it had sent two helicopters to help.
A spokeswoman said they were assisting Guernsey Coastguard with a search for a light aircraft off Alderney: “HM Coastguard helicopters from Solent and Newquay have been helping to search overnight with nothing found.”
The search and rescue operation had to deal with worsening conditions as they scoured the area on Monday night.
It is understood that the player returned to France after completing his move, and he was due to report for training in Cardiff on Tuesday ahead of next Tuesday’s Premier League game at Arsenal.
When his signing to Cardiff was announced, he said: “It gives me great pleasure and I can’t wait to start training, meet my new teammates and get down to work.”
Club chief executive Ken Choo said: “I’m sure all Cardiff City fans will join me in that and we can look forward to seeing our record signing in a Bluebirds shirt.”
The most recent tweet from Sala’s account was a picture of him and his former team-mates, captioned “La ultima ciao”, or “the last goodbye”.