It means you can book the returned flight option without providing an AWB number. Related ArticlesUsing Track & TraceAWB required to make booking12 Best practices for your airline APIsI put the airline prefix in the AWB field of my booking request, why was my booking rejected?I am getting an error informing me that my AWB number is wrong or not in my stock, but the AWB was provided by the airline itself. How can I fix this?