I repeat, we are in the middle of the ocean over international waters... For example, flying from US to UK and we are in German plane. Which country is responsible to execute arrest?
If you're over international waters, you're bound by the laws under which flag the ship or plane travels. So if you're over international waters in a plane registered to a US corporation, US law will apply. If you're flying on a Japanese airline, Japanese law will apply, etc.
the whole 'international waters' or 'high sea' just means that one country isn't allowed to impose rules upon other countries in those areas -- it doesn't mean that an individual is free to do whatever they want without get arrested.
(And keep in mind -- pretty much any plane carries air marshalls these days, which do have the authority to arrest you if you are disruptive enough)