Flying over water, at night, with no visual references, the pilots were unaware of their true altitude, and struggled to control and navigate the aircraft.

The investigation determined that the air data computers were unable to show correct airspeed and altitude on cockpit displays because a maintenance worker had failed to remove tape covering the pitot-static system ports on the aircraft exterior prior to departure.

[citation needed] This aircraft took off 42 minutes after midnight (05:42 UTC) on October 2,[1]: 10  and the crew immediately discovered that their basic flight instruments were behaving erratically, and reported receiving contradictory serial emergency messages from the flight management computer, including the altitude and airspeed indicator, rudder ratio, mach speed trim, overspeed, underspeed and flying too low.

As a consequence of the pilots' inability to precisely monitor the aircraft's airspeed or vertical speed, they experienced multiple stalls, resulting in rapid loss of altitude with no corresponding change on the altimeter.

The pilots desperately clawed for altitude and managed to get the 757 airborne again for 19 seconds, but due to the damage to the left wing the aircraft rolled over and slammed into the water near-inverted.

[2] Later investigation into the accident revealed that adhesive tape had been accidentally left over some or all of the static ports (on the underside of the fuselage) after the aircraft was cleaned and polished, eventually leading to the crash.

The blockage of all of the static ports is one of the few common-failure modes resulting in total failure of multiple basic flight instruments and, as such, is regarded as one of the most serious faults that can occur in avionics systems.

Such covers are commonly employed in aviation for blocking access to critical components when the aircraft is not in operation and are generally a bright color and carry flags (which may have "remove before flight" markings).

[12] As a result of the blocked static ports, the basic flight instruments relayed false airspeed, altitude and vertical speed data.

[12] The official accident report concluded that the flight crew, distracted by the conflicting warnings, did not heed the radar altimeter reading after descending through 2,500 feet (760 m).

[1] Mike Eidson, an American attorney, represented 41 passengers and crew in a lawsuit contending that the aircraft's manufacturer, Boeing, bore responsibility for the disaster, as the company ought to have foreseen the misuse of its products.

[2] After extensive[vague] litigation, the parties agreed to transfer the case against Boeing and Aeroperú to an international arbitration in Santiago, for a determination of the damages.

[14] On December 13, 1999, family members of the flight's passengers received one of the largest compensations stemming from an aviation accident outside the United States aboard a non-U.S. carrier, averaging nearly $1 million per victim.