A survey of the wreckage revealed that the tail was mostly intact and all control surfaces were connected to the pilots' controls. Both wings had been severely damaged on impact and fractured into several pieces. The flaps and slats were found in their extended positions, with the flaps set at 14°. As with the tail, all wing control surfaces were found to have been connected to the pilots' controls. There was no evidence of any control surface failure prior to the crash. Investigators realized that none of the four engines had been under power at the time of impact. As the first responders worked to rescue the passengers, investigators recovered the flight data recorder (FDR) and cockpit voice recorder (CVR) from the wreckage and brought them to the NTSB laboratory in Washington, D.C. The FDR was an older oscillographic foil model. In 1989, the FAA began requiring domestic carriers to change to digital flight recorders to minimize the errors that foil models produced. This requirement did not apply to international carriers. The Avianca FDR foil was found to have been taped down at some point prior to the flight and, thus, was inoperative. The NTSB recommended in the Avianca report that the FAA take an "active role in ensuring upgraded international standards" for flight recorders. The CVR and ATC recordings became vital sources of evidence for the crash. The investigators also looked at meteorological factors that led to flight problems.