Djerba Devil
You are mile off about the GSM 767's.
The aircraft are owned by ILFC.
They were not leased to NAS.
They were operated on a ACMI (Aircraft Crew Maintenance Insurance) contract.
This means that for a cost agreed by the two parties GSM would provide an insured a/c with crew and maintenance to NAS Air.
NAS Air would then in turn have to pay for everything else like fuel and airways costs, plus lots more.
They were out in Jeddah doing the Haj flights. With the crews (GSM's own crew) being based in Delhi.
It would require the owners permission to sub-lease an aircraft to someone else, but an ACMI contract does not, as it is still operated by GSM and their crews.
So NAS have nothing to do with the aircraft in question.
When GSM went under in December NAS were left in the limbo as they had a contract for airframes with an airline that no longer existed.
Maybe because of this they were non to kind to the GSM crew stranded in Jeddah. It was a very fraught few days for the staff out there as NAS were refusing to repatriate them and had their passports, as per Saudi law.
The crews eventually, after cash was paid by the administrators, got to Delhi, from there Virgin flew them back for next to nothing.
On arriving home in the UK they had no job all this the week before xmas.
At least I was at home when the company went under.
Why they are on the Jet2 list of a/c is beyond me, but your last two paragraphs are utter and complete b******s.