There is no actual duty or vat payable on inter EU purchases.
Is that true?
If I (UK VAT registered business) sell something to a French customer, I have to charge him 20% VAT, unless he supplies me a French VAT number.
The only way that a French non VAT registered person could buy a plane from say the UK, free of VAT, is if the seller was
not a VAT registered individual or business.
Any such plane will be more expensive than "plus VAT" ones, because the first non VAT registered person/business that owned it had lost the VAT on it so they had to sell it on at a higher price. In essence there are two markets for planes: ones which are "VAT paid" and ones which are "plus VAT".
What happened a lot in the past was that Joe Bloggs went to the USA, bought a plane there, flew it to the UK, possibly but not necessarily put it on the G-reg, but never paid the import VAT.
There was a VAT amnesty, IIRC, in the 1980s, which drew a line under that, but after that you were vulnerable to getting hit for the VAT.