Officials of the Nigerian Airspace Management Agency (NAMA) are to be interrogated by the State Security Service (SSS) for allegedly doctoring the transcript of the voice flight record of the pilot of the missing Beechcraft plane and the Port Harcourt Airport control tower.

The Federal Government gave the directive based on the discovery by the Technical Committee President Umaru Yar'Adua set up to investigate the disappearance of aircraft in March.

Those to be questioned are NAMA Managing Director, Ado Sanusi; Air Traffic Services Director, Olopha B. Stephen; Technical Services Director, B. Eze; and Search and Rescue General Manager, A. Adedara.

A Presidency source confirmed on Monday that the committee discovered that the tape of the conversation between the pilot and the airport tower was erased after the accident.

"To validate the scripts, the committee requested for the voice tapes from which the transcripts were made. However, to the dismay of the committee, it was discovered that the Port Harcourt Airport voice tapes were tampered with, which has made the committee's work very difficult," the source said.

The committee discovered that Air Traffic Controllers (ATCs) at the Port Harcourt Airport apparently misled the pilot, which could have been responsible for the accident.

It was also learnt that although the airline has its own procedure and charts on how to get to Bebi Airstrip in Cross River State, the captain opted for the official NAMA route apparently because he had not flown to the airstrip before.

"According to information available to us, the Port Harcourt controller told the pilot to contact Enugu tower, but the pilot initially refused and insisted on flying the NAMA route which would take him straight to Bebi. He contacted Enugu later and the controller said he had traffic and cleared him to descend to 5,000 feet.

"From a professional point of view, it is clear that the controllers do not know the topography of the area in which the missing plane was flying. That was why the flight was cleared for 5,000 feet by the Enugu controller. Bebi sits behind a 6,000-foot mountain. The minimum safe height at that position is 11,200 feet."

Meanwhile, the Nigerian Civil Aviation Authority (NCAA) has sought the active collaboration of all global aviation agencies on the prevention of air mishaps.