On October 20, 1965, the flight departed from Manila's Runway 13, when the aircraft began slowly but gradually banking and veering to the left.

The aircraft was a Douglas DC-3 (C-47A-25-DK) manufactured in the United States and had its first flight in 1944, registered as 42–93486 before being delivered to Philippine Air Lines and re-registered as PI-C144.

The manifest prepared by company personnel and signed by the crew contained an error, which when corrected, exceeded the maximum trip payload by 83 kg.

When the aircraft reached 150 feet, at a heading of 050° and an airspeed of 85–90 mph, the left bank and turn was momentarily checked and the right rudder pedal was applied.

At this time the left wing struck a branch of an aguho tree before proceeding in a nose-down altitude, striking an electric post at a 30° angle and nosed over.

Various technical examinations and inspections conducted on the airframe, power plants and their components and accessories did not reveal any evidence of failure prior to the accident.

When the airspeed decreased, the pilots managed to move the right rudder pedal forward and the left turn and bank were corrected.

Although the pilots testified that they performed the normal pre-flight inspection and observed the pre-takeoff checklist, the Board believed that the rudder trim tab had been deflected prior to takeoff.

The fact that the aircraft was loaded slightly above its allowable gross takeoff weight, the testimony that the landing gear was retracted late, and the carburettor airscoop level locked between the hot and cold position, which could've reduced engine power, when considered separately may not have significantly affected the low altitude reached, but if these facts were considered altogether, including the bank of the aircraft which did not exceed 45°, they could've caused the low altitude during the flight.

[4][5] As a result of the investigations, the Civil Aeronautics Administration determined that the probable cause of the accident was the failure of the pilots to set the rudder trim tab to the proper position before takeoff and during the flight.

The continuous left turn and bank resulting in the crash was due to the undetected deflection of the rudder trim tab.