Puff,
The important thing to remember about this is the aircraft was painted in HC's colours,
Logo and phone number painted on it, had HC's flight number (HC675),
was handled and dispatched by HC at all ports, and tickets were just sold by HC.
HC was not selling tickets on a Transair flight for or on behalf of Transair. It was selling tickets on HC675, what was effectively its own service.
Effectively, HC had operational control of an aircraft and crew wet leased on a permanent basis, and a duty of care to ensure that standards were in place and achieved.
These matters will ultimately be tested.