The Manx2 plane which crashed at Cork Airport killing six people was put through a full maintenance check in Spain last week.
Airline chairman Noel Hayes said he was absolutely satisfied the flight crew - co-pilot Andrew Cantle from York and Spanish pilot Jordi Gola Lopez - were fully qualified.
Their full training records and qualifications have been passed to inspectors at Ireland's Air Accident Investigations Unit.
"The last 24 hours have been a very long and dark 24 hours for me but I know they were probably a longer and darker 24 hours for the families of the bereaved and my heart goes out to them," Mr Hayes said. "I offer my sincere condolences for yesterday's tragic accident."
Arriving at Cork Airport, Mr Hayes said the doomed 19-year-old Fairchild Metroliner aircraft had been inspected last week but he declined to comment on whether it was properly equipped to land in dense fog.
Mr Hayes signed a book of condolence at the airport before travelling to see four survivors at Cork University Hospital along with Northern Ireland Deputy First Minister Martin McGuinness. Outside the hospital the Irish Tricolour, the Union flag and the Spanish flag flew at half mast as a mark of respect for the six dead.
The victims included Brendan McAleese, 39, a businessman in Co Tyrone who was a cousin of Irish President Mary McAleese's husband Martin.
English co-pilot Andrew Cantle, 27 and originally from Sunderland but living in York, also died. He had only been flying with Manx2 for a fortnight. Another of those killed in the crash was Pat Cullinan, originally from Omagh, Co Tyrone, a partner in leading accountancy firm KPMG in Belfast.
Among the other victims was Captain Michael Evans, deputy harbour master in Belfast. Another British citizen, Richard Noble, originally from Derbyshire but living in Northern Ireland, also died. The pilot, Jordi Gola Lopez, from Spain, also died.
The survivors of the crash were Donal Walsh, from Waterford, Laurence Wilson, from Larne, Brendan Mallon, from Bangor, Barbara Elliot, from Belfast, Peter Cowley from Glanmire, Co Cork, and Mark Dickens from Watford but a Northern Ireland resident. They remain in a serious condition with two in intensive care.