Pakistani authorities launched a search operation after a cargo aircraft carrying five crew members disappeared off the coast of Karachi while en route from the United Arab Emirates, officials said Wednesday.

The Boeing 737 lost contact with air traffic controllers at 21:21 local time (16:21 GMT) on Tuesday after departing Sharjah for Karachi, according to Pakistan’s airport authority. Officials said the aircraft rapidly descended before communications were lost.

A problem with the aircraft’s navigation system had been reported shortly before it disappeared. Flight-tracking data from Flightradar24 showed the plane experiencing sharp altitude fluctuations before entering a steep descent.

Pakistani officials said the country’s navy and air force are conducting a search for the missing aircraft.

The plane was operated by K2 Airways, a private cargo carrier based in Karachi.

In a statement issued Wednesday, the airline identified the five crew members aboard the aircraft and said it was working with investigators.

“We continue to pray, earnestly, for the safety of our colleagues,” the airline said.

K2 Airways added that it was “fully cooperating with the Pakistan Civil Aviation Authority and other government agencies” as the search effort continued.

Officials have not announced what caused the aircraft to disappear, and no information was immediately available regarding the fate of the crew.

The aircraft entered service with K2 Airways in 2024 after operating for several airlines over more than two decades.

The Boeing 737 first flew for the Russian airline Aeroflot in 1999 before later operating for Garuda Indonesia beginning in 2004. It was converted into a cargo aircraft in 2012 and subsequently flew for TNT Airways and ASL Airlines before being transferred to a Pakistani operator.

Most recently, the aircraft had been used to transport cargo throughout the Arabian Gulf and the broader region.

The search remained ongoing Wednesday as Pakistani military and civil aviation authorities continued efforts to locate the missing aircraft and determine what happened during its final moments before radar and communications were lost.