A.
In regard to Medical Oxygen Cylinders, as stipulated in DGR 2.3.4.1. carriage as checked or carry-on baggage is possible with approval of the airline (operator).

Cylinders with gross weight exceeding 5kg, and cylinders using liquid oxygen are forbidden for carriage as baggage. Loaded quantity and location must be advised to the pilot-in-command. Cylinders with gross weight exceeding 5kg are forbidden as baggage. It does not mean cylinders with less than 5kg gross weight may automatically be permitted as baggage. Please do not misunderstand the rules. The cylinders must clear all the conditions stipulated in DGR 2.3.4.1 and must be approved by the carrier to be permitted as baggage.

Furthermore, there are a number of operator variations to Medical Oxygen Cylinders. It is advisable to check the operator variation of the carrier to be used.