Someone needs to introduce @JLongworthLML (a) to rules of origin and the difference between a CU and zero tariffs and (b) to basic points about how the single market works. 
As for this rather Leninist tweet by @JLongworthLML, any company which has decided to base production here on the basis of genuinely frictionless access to the rest of the EU would be rather foolish if it wasn’t now reconsidering its business model.
Indeed, this explanation of the issues from Airbus more or less reflects the legal advice that I would give. airbus.com/content/dam/ch…
For @JLongworthLML to regard it as scaremongering or (in words of which Lenin would be proud) an anti-democratic conspiracy, demonstrates nothing apart from his own failure to understand, or be honest about, the issues.
And as @hhesterm points out, the consequences of ignorant and silly attacks of this kind are bad for all of us: except perhaps the ignorant attackers themselves.
PS - NB this point from @SamuelMarcLowe on the claim that aviation products are zero-tariff.
