material available date in cross-company business

Hello guys,

I encountered a question in <b>cross-company business</b>.

1. create PO with ME21N;

2. create outbound delivery against PO with VL10B.

I found material available date in outbound delivery is always the same as delivery date in PO. why? by my understanding, material available date should got base on ATP.

could you give me any suggestion?