ISLAMABAD — Pakistan's Navy and civilian authorities expanded their search Wednesday for a cargo plane feared to have crashed into the Arabian Sea after it disappeared from radar and lost contact with air traffic control late Tuesday night while flying from Sharjah, in the United Arab Emirates, to the southern port city of Karachi.

The Karachi-bound aircraft, a Boeing 737-400 freighter operated by the private carrier K2 Airways, reported a navigational system issue while en route with five people on board. According to the Pakistan Airports Authority, the aircraft was being guided by the Karachi Area Control Centre after reporting the fault at 9:18 p.m. local time. Three minutes later, at 9:21 p.m., the aircraft was observed on radar making a rapid descent accompanied by a sharp change in heading. Radar contact and communication were lost shortly afterward, approximately 155 nautical miles, or 287 kilometers, west of Karachi.

Preliminary flight-tracking data reviewed by multiple outlets showed the aircraft losing nearly 1,525 meters, or roughly 5,000 feet, of altitude in under a minute before climbing back approximately 1,830 meters, or about 6,000 feet, over the following 30 seconds. It then entered what flight-tracking service Flightradar24 described as a final, near-vertical descent from a height of 11,140 meters, or about 36,550 feet. The aircraft's last transmitted position placed it at 335 meters, or roughly 1,100 feet, descending at 22,400 feet per minute, or approximately 400 kilometers per hour, a rate of descent consistent with the plane entering the water.

The Pakistan Airports Authority said it activated its Rescue Coordination Center immediately........

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