Article 31 of the Chicago Convention (also known as the Convention on International Civil Aviation) concerns the transfer of aircraft from one operator to another. Article 83 bis is an additional provision to article 83 of the Convention, which relates to the registration of aircraft.

If a transfer agreement between operators excludes Article 31, it would mean that the transfer of the aircraft is not taking place in accordance with the requirements of the Convention. In this case, the transfer agreement would not be considered valid under the Convention.

It's important to note that the Chicago Convention sets the standards and recommended practices for civil aviation, but it's not the only international agreement that regulates aircraft registration and transfer. The specific laws and regulations of the countries involved in the transfer will also play a role in determining the validity of the agreement. It would be recommended to consult with legal experts in the field to determine if the transfer agreement is compliant with all the relevant laws and regulations.