cribbagepeg, near the end of phase 3, some of the assets being used had to hurry off because there was an oil well in the Gulf of Mexico spewing great amounts of oil.
For phase 4, the current search, the BEA relied in large part on analysis by a company outside of Washington DC, named Metron. Woods Hole which did the actual search used three remote-controlled submersibles. In the BEA's view, Woods Hole was chosen because they are the best in the world at this sort of deep ocean reconnaissance.
http://www.bea.aero/fr/enquetes/vol....h.analysis.pdf
For phase 3, the principal reliance was on the analyses of the so-called drift group.
http://www.bea.aero/en/enquetes/flig...oup.report.pdf
Neither new sonar analysis or the availability of new submersible technology had anything to do with phase 4.