The 27-year-old Boeing was the only plane in the fleet of the Karachi-based K2 Airways private cargo airline. Photo: Handout/K2 Airways

The Karachi-bound 737-400 plane operated by a Pakistani carrier took off from Sharjah in the United Arab Emirates and lost contact with air traffic control about 9:18pm (16:18 GMT) on Tuesday after reporting a navigational ⁠system fault, the Pakistan Airports Authority said.

Minutes later, data from Flightradar24, a global flight-tracking service, showed the plane losing nearly 1,525 metres (5,000ft) of altitude in less than a minute before climbing about 1,830 metres (6,000ft) in the next 30 seconds. It then entered a final, near-vertical descent from a height of 11,140 metres (36,550ft).

Its last transmitted position placed it at 335 metres (1,100ft), descending at 22,400 feet per minute, or about 400 kilometres per hour. All contact was lost about 155 nautical miles (287km or 178 miles) west of Karachi.

Security sources told Al Jazeera a Pakistani navy ship, a merchant vessel operated by the Pakistan National Shipping Corporation and two navy aircraft are taking part in the search.

No wreckage or survivors have been found so far.

“We continue to pray, earnestly, for the safety of our colleagues,” K2 Airways, the Karachi-based private cargo airline that operated the flight, said in a statement on Wednesday, adding that it was fully cooperating with authorities on the search.

It was the only plane in the K2 Airways fleet.

If a crash is confirmed, the incident would mark Pakistan’s first major civilian air disaster since May 2020 when a Pakistan International Airlines plane crashed short of the runway in Karachi, killing 97 of the 99 people on board.

The 27-year-old K2 Airways’ 737-400 has flown for six operators.

Delivered to Russia’s Aeroflot as a passenger aircraft in 1999, it later flew for Garuda Indonesia before being converted into a freighter in 2012 for Belgium’s TNT Airways.

Aircraft tracking records show it was withdrawn from service in June 2023 and parked in France for about 10 months.

Irish company AerCap reactivated the aircraft in April 2024 before placing it back into storage, first in Jakarta and later in Karachi, where it remained for nearly six months before entering service with K2 Airways in December 2024.

In a statement, Pakistani Prime Minister Shehbaz Sharif expressed grief over the incident and offered his sympathies to the families of the missing crew members.