Location of Aircraft Register
Remember that there is an important distinction between the jurisdiction of the legal owner of the aircraft, the place of registration of the aircraft and the jurisdiction of the operator and their air operator certificate.
The jurisdiction of the legal owner of the aircraft is often (but not always)dictated by where the aircraft will be registered (e.g. FAA N-reg aircraft generally need to be owned by US-incorporated companies, financiers or trustees, but there are ways around this).
The place of the register (for airliners, at least) is dictated frequently by the ease of registration (and enforcement) of the aircraft mortgage in that jurisdiction by a financier. Ireland is particularly popular given that it is a signatory to the Cape Town Convention and it is very easy to register and if necessary enforce a mortgage over the aircraft and retake possession. I would shudder to think how painful it would be to enforce a mortgage over an aircraft registered in Russia (for example). It’s actually messy to enforce an aircraft mortgage in many European jurisdictions (Italy is just one example), hence why Ireland is such an attractive place to register an aircraft.
Some US banks often feel more comfortable registering the aircraft in the US and taking a US-law mortgage, hence why you sometimes seem random foreign airlines with N-reg aircraft (often the case for aircraft operating in South American or the Mid-East)
(in the past there was also the “double-dip” and “triple-dip” tax-driven leasing structures that would involve ownership and/or registration and/or lessee or lessor in Germany and Japan, but these are pretty hard to achieve these days so aren’t a big factor anymore)
The jurisdiction of the operator is a whole different kettle of fish to where the aircraft isregistered, which is what I think people are most worked-up about.
The lien over an aircraft for unpaid Eurocontrol ATC and nav charges which a few people mentioned is levied on the aircraft regardless of where it is registered – whether the aircraft is registered within the EU or outside the EU makes no difference for Eurocontrol.
Flags of convenience for the shipping industry and the location of the register (and employment terms of those working on the ships) function differently to aircraft, so the comparisons aren’t quite the same.