The plane was operated by Zeusch Aviation, based at Lelystad Airport in the Netherlands, which has confirmed it is “actively supporting the authorities with the investigation”.
The aircraft had flown from the Greek capital Athens to Pula in Croatia on Sunday before heading to Southend. It was due to return to Lelystad on Sunday evening.
BBC reporter Sofia Bettia has been at the headquarters of Zeusch Aviation – a privately owned company operating 14 aircraft.
“This is a small airport in the Netherlands, on an island to the east of Amsterdam – and today, it is almost deserted.
“We just saw airport security staff lowering the Dutch flag to half mast at the entrance of the airport.
“Zeusch specialises in medical evacuation flights, private charters, and aerial filming for various events.
“We were able to speak to a pilot from another airline. He told us he’s worried that one of his colleagues may be among the victims, as many of the staff here know one another.”