Even if you know exactly where the airplane broke up, finding debris can be very difficult:
* There often aren't many big pieces left after a breakup at 550 MPH.
* The debris is falling 7 miles, so where it actually lands is pretty random and dependent on the shape / weight of the debris. Lower density debris probably travels further.
* Most debris sinks when it does get to the ocean.
* The lower density debris that floats moves in currents.
* You can't search at night, so the floating debris might move considerably before you can start searching.
* There often aren't many big pieces left after a breakup at 550 MPH.
* The debris is falling 7 miles, so where it actually lands is pretty random and dependent on the shape / weight of the debris. Lower density debris probably travels further.
* Most debris sinks when it does get to the ocean.
* The lower density debris that floats moves in currents.
* You can't search at night, so the floating debris might move considerably before you can start searching.