This is a very serious issue, and lots of questions needed to be answered by the Americans and Pakistani authorities.
1- His body must have either been flown from north, i.e. from Abbotabad to Karachi and from there taken to the sea by a naval vessel. This means that American navy was already stationed in Karachi.
2- Or his body was taken to Afghanistan and flown from there to the sea, either route through Pakistan or from Central Asia to a naval vessel somewhere in either Caspian or Mediterranean Sea. In either case, permission is granted for Air Passage by either Pakistan or a group of nations if Central Asia. This needs planning and permissions in advance.
3- Considering it would be easier to have the arrangements with one nation, Pakistani route is more likely.
4- Americans know, the world will ask for proofs. They ought to have taken pictures and shoot video footage of his corps. If they did, it should be surfaced soon with fanfare in American media.
5- Musharaf the traitor just said on ARY that Americans may have not wanted to bury him on land because it would cause problems in the future, therefore they decided to dispose of his remains either the corps or ashes if he is cremated, which according to the news that he was possibly given a Muslim last rites.
6- If no pictures and hopefully video footage of his corps is not shown to the world, then this whole episode is questionable and smell of conspiracy theories is in the air, already. Like they say in Urdu, "Dal me kooch Kala he", I think the whole of the dal is black in this case, rotten.
Dont expect Pakistani reaction to get any answers, it is reported a high power meeting was held in President House attended by the President, Prime Minister, COAS, ISI, IB, AI chiefs. The press release is issued after the meeting, but it does not give any answers.
Troubles, troubles on grand scales, be prepared.
