What Law Applies when travelling between two countries on a plane?

What Law Applies when travelling between two countries on a plane?

Traveller.com, Friday Jan 12: In most situations, it’s the law of the country where the aircraft is registered that applies on board. Thus a United States passenger aged 18 travelling aboard a Qantas aircraft in US airspace can legally drink alcohol, even though US law stipulates a minimum drinking age of 21. However, there are anomalies. A passenger found to be in possession of illegal drugs on a Singapore Airlines flight from Singapore to Frankfurt would be prosecuted under German law, not Singapore’s. Read more on Sydney Morning Heralds Travel site