Cardiff City paid tribute to Mr. Sala on Tuesday, at its first match since he disappeared, against Arsenal in London. Players and staff wore daffodils in his honor, and his name was included in the team roster in the match-day program. Both Cardiff and Arsenal, which won the match, laid floral tributes to Mr. Sala at Emirates Stadium.
At several English Premier League matches this week, the teams observed a moment of silence in memory of Mr. Sala.
“It is very difficult to even describe how the players are feeling,” Sol Bamba, a Cardiff defender, told BBC Sport Wales.
“We have all been affected by it — the lads, the city, the whole club.”
News reports have questioned whether Mr. Ibbotson should have been piloting the plane. He held a private pilot’s license in the United States, and his medical certification was up to date, according to records on the Federal Aviation Administration’s website.
But to fly the plane in Britain with a paying passenger, Mr. Ibbotson needed a commercial pilot’s license, and to fly at night, he needed a so-called instrument rating. Britain’s Civil Aviation Authority would not comment on Mr. Ibbotson’s credentials, but the authorities said the investigation into the plane’s disappearance would cover personnel records.
The flight went through rough, wintry weather over the Channel, and Mr. Sala left a voice message for friends and relatives saying that he was afraid that the plane would break apart.
“This would not have posed a problem for a pilot with a current instrument rating, but difficult for a pilot without one,” David Learmount, a former flight instructor, said in an email.