The pilot, Chris Phatswe, took off from Gabarone's Sir Seretse Khama airport on Monday and circled in an empty ATR-42 for almost two hours.

Officials said he radioed the control tower and announced: "I intend to kill myself."

There followed a desperate conversation between the emotional pilot and Botswanan officials in the tower.

Deputy commander of Botswana's Defence Force, General Tobogo Masire, led efforts to talk Phatswe down.

As the plane ran short of fuel, Phatswe threatened to crash it into an Air Botswana office building to settle an apparent grudge with the airline's management.

The pilot had demanded to speak to Botswana's Vice-President Ian Khama and "was about to be put through to his office when the plane ran out of fuel," said Air Botswana general manager Joshua Galeforolwe.

It was unclear what Phatswe's demands might have been.

After being told by the control tower that there were people in the Air Botswana building, Phatswe crashed the plane into two other ATR-42s on the tarmac, destroying the aircraft and himself in a fireball.

There were no other casualties, Botswana's Department of Civil Aviation said.

Grounded

Phatswe had been grounded due to ill health, and took the plane without permission.

"He was grounded because in the view of Air Botswana he was unfit to fly," said John Williams, the national carrier's commercial manager.

He refused to elaborate on the reasons for the decision until an inquiry is complete.

Sources quoted by Reuters news agency said that Phatswe had repeatedly warned airport authorities that he was going to kill himself.

A private pilot at the airport quoted by the Agence France Press news agency said security was very lax and that it would have been easy for the pilot to gain access to the aircraft.

Flights cancelled

Air Botswana operations have been crippled, as the airline only has one plane left - a BAe-146 which is grounded with technical problems.

There was panic in the airport terminal where about 50 passengers in the terminal waiting for flights to Johannesburg, Harare and the Botswanan town of Francistown.

They were evacuated as Phatswe circled overhead and buzzed airport buildings.

"He was going over and over. Airport staff chased everybody out. I hid behind a counter," said one passenger.

All flights were cancelled due to lack of serviceable aircraft.