Cardiff's executive director Ken Choo has expressed his shock and distress at hearing the plane carrying new striker Emiliano Sala has gone missing over the English Channel.
Sala, 28, was on his way back to Wales after saying goodbye to his Nantes team-mates on Monday night when contact was lost with the aircraft.
Choo said in a statement: "We were very shocked upon hearing the news that the plane had gone missing. We expected Emiliano to arrive last night into Cardiff and today was due to be his first day with the team.
"Our owner, Tan Sri Vincent Tan, and chairman, Mehmet Dalman, are all very distressed about the situation."
Choo added: "We made the decision first thing this morning to call off training with the thoughts of the squad, management staff and the entire club with Emiliano and the pilot.
"All of us at Cardiff City FC would like to thank our fans, and the entire footballing family for their support at this difficult time.
"We continue to pray for positive news."
Sala had signed a three-and-a-half year deal with the Welsh club after scoring 12 Ligue 1 goals in 19 appearances this season.
Choo described Sala as a "great person" and revealed he had been "so happy" to sign for Cardiff.
He said in an in-house TV interview: "You could see from his face he is so, so happy to be here and ready to start.
"Words cannot describe the look on his face when he met us, we walked him around the ground, he was absolutely ready to give it a go.
"We really feel sad to hear of this news because we met such a great person."
Choo revealed Sala had described joining the Bluebirds as "one of the best days of his life".
Cardiff have been in contact with Sala's family as they wait for news.
Choo said: "We are waiting for (French aviation authorities) to inform us. We are trying to communicate with them, the agent of the player and the family.
"We like to reach out to the family because it's a very tough time.
"At this point in time we just want to know if he and the pilot are OK."
Cardiff City Supporters Club spokesman Vince Alm said: "The reaction is one of shock, devastation and concern.
"You just think of a young man making a career move that he had probably dreamed of all his life. Hope is obviously fading as time goes on."
Nantes president Waldemar Kita added on the French club's website: "I'll always have hope, he's a fighter. It's not over, maybe he's somewhere."
The French civil aviation authority said Sala was aboard a light aircraft that disappeared from radar en route from Nantes to Cardiff.
Rescue teams were scrambled to waters north of Guernsey after the light aircraft carrying two people vanished, Guernsey Police said.
Searches of the area resumed on Tuesday morning, with authorities saying the missing plane had yet to be found.
Guernsey Police said the Piper PA-46 Malibu, a single turbine engine aircraft carrying two people, departed Nantes at 7.15pm for Cardiff and was flying at an altitude of 5,000ft.
On passing Guernsey it "requested descent", but Jersey air traffic control (ATC) lost contact with the plane while it was flying at 2,300ft.
Guernsey Coastguard received an alert at 8.23pm from Jersey ATC that a light aircraft had gone off their radar approximately 15 miles north of Guernsey.
A major search and rescue operation was triggered involving both St Peter Port and Alderney lifeboats and the Air Search 1 and two HM Coastguard helicopters.
Guernsey Police revealed in a update before midday on Tuesday that over 1,000 square miles had been searched by five planes, but no trace of the missing plane had been found and the search was continuing.
Guernsey Police confirmed in the afternoon that "two planes, two helicopters and a lifeboat" were searching for the missing aircraft but that "no trace had been found".
That statement also said that conditions for the search had been difficult overnight but had improved.
"Today the sea is much calmer, although visibility was good, it is now deteriorating," the statement read.
"UK authorities have been calling airfields on the south coast to see if it landed there. So far we have no confirmation it did.
"Search continues. Decision at sunset about overnight search."
Nantes' Coupe de France clash with third-tier Entente Sannois, scheduled for Wednesday evening, has been postponed until Sunday.
A statement from Sannois' official website read: "Sannois wish all the best to Nantes and to the family of Emiliano Sala at this challenging time.
"The club is also thinking of all the people on board the plane."
Sala, a native of Santa Fe in Argentina, played at youth level for Club Proyecto Crecer in his home country before being snapped up by French club Bordeaux in 2010.
He was then sent out on a series of loans to Orleans, Niort and Caen and after failing to make more than a handful of appearances for Bordeaux, Sala joined Nantes in 2015.
It was in Brittany that his career began to flourish.
Sala's hat-trick against Toulouse in October 2018 was the first by any Nantes player in Ligue 1 since 2006.
Cardiff signed the forward in a deal reportedly worth in the region of £15million, breaking the previous record of £11million paid for Gary Medel in 2013.
