How can they track sharks for thousands of miles of ocean but can't track an airplane?

They lose 3 out of every 5 sharks too.

Water is the most difficult, troublesome domain for humans.

I believe they put some sort of tracking device on the sharks,but its a different thing really. I have rushed you this link to a news item from the online mail saying they are sure it was a hijack. They know it and is searching the home of the pilots. In this sea there are hundreds of islands it could have been taken.

I think there were pilots on board who had turned off all the systems.

Like somebody has already said it did have a tracking device on it but for some reason the crew turned it off.

Maybe it might be a good idea to make these tracking devices permanently on and out of the control of the crew.

The shark had a tracking device on it, the plane didn't after the crew turned it off.

If the shark was smart enough to turn off the tracking devise attached to it, you wouldn't be able to track Jaws either.