The BBC suggest the long haul a/c will be a Boeing 727. Both will be leased, like our new hospitals but second-hand. IMO should be replacement a/c for Queen's Flight (not very New Labour), flown and maintained by RAF.
Could have got a good discount on an Airbus or reduced fares from recently-gonged Stelios.
How about a new Royal Yacht for State visits and foreign entertaining. Savings on 5 star hotel bills would soon pay for it.