Compensation under Carriage by Air Act not treated as property for estate duty purposes; accident insurance proceeds remain dutiable. Compensation under the Carriage by Air Act paid to heirs after a passenger's death does not constitute property passing on death for estate duty because it arises only after death, is not in the deceased's possession or control during life, and the deceased had no interest or power of disposition in it. The principle extends to the 1972 Act and notifications. Conversely, accident insurance sums represent an interest existing in the insured's lifetime that can pass on death and are chargeable to estate duty.