One could look upon certain aircraft types being put on a foreign register when operating in a different country as using a 'flag of convenience'.
Whilst there may have been an element of that here, I understand that the aircraft was HA registered because all the expertise in maintaining this type was in Hungary. That's fair enough.
The AAIB's investigation will be interesting to follow and this comes quite soon after the CAA's ongoing work, subsequent to an AAIB Safety Rec, concerning the operation of foreign registered aircraft based in the UK.
The investigation will hopefully be assisted by the accounts of the survivors, having witnessed those last few seconds before impact.