The Bhoja Air plane that crashed near the Pakistani capital went into a sudden dive shortly before it disappeared from the radar screen and slammed into the ground, a senior aviation official said on Saturday.

Bhoja Air's flight B4-213 from Karachi to Islamabad suddenly dropped from 2,900 feet to 2,000 feet after it was cleared to land at the Benazir Bhutto International Airport on Friday, Civil Aviation Authority Director General Nadeem Yousufzai told a news conference on Saturday.

"It just went down into a dive...that has to be investigated. What was the reason, was it a downdraft or an engine failure?" he said. The reason for the dive would be established by the investigation that has been ordered by the government, he added.

All 127 people on the plane were killed when it crashed in bad weather in Hussainabad village, located less than 10 km from the airport. This was the second major air disaster near the Pakistani capital since July 2010, when an Airbus of private carrier AirBlue crashed into the Margalla Hills, killing all 152 people on board.

Yousufzai said the Bhoja Air Boeing 737-200 that had crashed had been certified by the CAA. The airline too was operating in accordance with prescribed procedures.

"There was no compromise on safety standards," he said.

Bhoja Air was recently revived after being closed for over a decade due to financial problems. Media reports said the airline has a fleet of ageing aircraft, mostly Boeing 737-200s.

Yousufzai said Bhoja Air's revival had been cleared by the CAA only after the airline had paid all its outstanding dues and all its aircraft had been certified. He said no political pressure was involved in the airline's clearance.

The National Transportation Safety Board of the US and the aviation firms Boeing and Pratt and Whitney will be involved in the probe into the crash, Yousufzai said.

The aircraft was made by Boeing while its engines were manufactured by Pratt and Whitney. Earlier in the day, Meteorological Department director Arif Mahmood told the media that his organisation had issued two warnings about bad weather at 3 pm and 6 pm on Friday.

Both warnings were valid for three hours and were issued due to heavy cloud cover over the airport.

Mahmood contended that no flights should have been allowed to operate in such weather and they should have been diverted to Lahore.

"There were high wind speeds and gusts of up to 65 knots or 100 kmph. In such a downdraft, it would be difficult for anything to survive," he said.

However, the CAA chief contended that the weather warnings were not so severe that the Rawalpindi airport should have been closed.

Meanwhile, Geo News channel quoted its sources as saying that a preliminary investigation had revealed that the plane had caught fire before it crashed and this may have been due to lighting striking the aircraft.

It reported that the record of the conversation between the pilot and the control tower had been sealed.

Other reports said that the Bhoja Air plane which crashed was 28 years old and had been bought on dry lease from a South African company.

The aircraft was recently cleared to fly by aviation authorities after tests in South Africa.

Bhoja Air's licence was restored in March and the aircraft that crashed was on the firm's maiden evening flight from Karachi to Islamabad.

The pilot of the flight, Noorullah Afridi, and first officer Javed Mushtaq were both retired air force personnel.