CAB 18900 (the Montreal Agreement) records the understanding reached in 1966 between the United States Government and the international airline community being the price extracted by the former in consideration of its preparedness to remain an adherent to the Warsaw Convention despite dissatisfaction with the level of liability limits for passenger claims. Air carriers who became party to the Agreement (those that wished to continue to participate in the avaiation commerce of the U.S.) agreed that by special contract with their passenger customers they would voluntarily accept two modifications to the terms of the contract of carriage as otherwise imposed by the Convention—at least, that is, with respect to carriage to, from, or with an agreed stopping place in the U.S.

First, the Convention limits of liability for death or injury (effectively $10,000 under the original 1929 treaty and $20,000 under the 1955 Hague Protocol amendments never ratified by the U.S.) were to be increased by means of the special contract to $75,000, or to $58,000, plus legal costs, in jurisdictions where provision was made for separate awards for costs. Second, the air carrier agreed to waive reliance upon the art. 20(1) defence to liability that it had taken all necessary measures to avoid the occurrence or that it was impossible to take such measures. The basis of liability was thus raised from strict to near absolute with contributory negligence as the sole residual defence.

While the substantive obligations created by the Montreal Agreement were clear, CAB 18900 also stated that:

There followed three paragraphs of some 270 words designed to warn of the carrier’s right to limit liability but drawing attention to the ameliorating effect of the 1966 understanding.