Inoperative ACAS

[fishlips]

I don't know whether this question should be placed here or not. If not, please tell me 'where I should go' to ask.

Does most countries require ACAS to be operative before being allowed to land in a country? This incident occured to me today at work and I was all question marks. A flight was about to leave SIN for HKG with ACAS inoperative and from what I heard, an exemption was granted only to be over-ruled and required an explaination from the airline.
I would appreciate if all the professionals out there will clear the air up for me. Many thanks.

[Capt Pit Bull]

Can't give you a cast iron world wide answer, but as a UK based short haul operator our MEL allows operation with TCAS inop for up to 10 days.

CPB