The wreckage of K2 Airways cargo Boeing 737 was recovered 98km south of Ormara port, Pakistan Airports Authority said.
Pakistan navy and Pakistan Maritime Security Agency deployed "various air and sea borne assets" to locate the remains, it said, adding that the search operation was continuing to find the crew members.
The aircraft had departed from Sharjah in the United Arab Emirates and reported a navigational system problem before losing contact with air traffic control.
Prime Minister Shehbaz Sharif had directed authorities to speed up the search for the 27-year-old converted freighter, which went missing in the Arabian Sea after reporting a navigational system problem.
K2 Airways, the plane's operator, said the crew comprised two pilots, two engineers and one support staffer.
Authorities have made no official declaration on their status although Sharif expressed his "heartfelt condolences" to their families.
The plane may have crashed into the sea southwest of Karachi after a series of sharp altitude changes before a steep final descent, according to flight-tracking service Flightradar24.
Authorities had launched a co-ordinated search and rescue operation at sea through various agencies, the airports authority said.
K2 Airways said it was co-operating with the Pakistan Civil Aviation Authority and other government agencies.
Boeing has not yet commented.
The plane reported a navigational system issue at 9.18pm while flying towards Karachi, the airports authority said.
Local air traffic control tried to guide it but three minutes later radar systems showed the plane descending rapidly and communication was lost, the authority said.
The flight was about 285km west of Karachi at the time, according to the statement.
The final minutes of Flightradar24's tracking data appeared chaotic, showing the plane plunging about 5000 feet in less than a minute before soaring about 6000 feet in 30 seconds and then entering a catastrophic dive from 36,550 feet.
The last transmitted data point placed the aircraft at 1100 feet above sea level, with a vertical rate of minus 22,400 feet per minute - about 400km/h - an extremely steep and abnormal rate of descent.
The missing aircraft is one of Boeing's decades-old 737-400s, two generations older than the 737 MAX that has been involved in a safety crisis.
It uses engines made by CFM International, jointly owned by GE Aerospace and France's Safran.
The 737-400 was first delivered as a passenger plane to Russia's Aeroflot in 1999 and was converted to a freighter in 2012, according to Flightradar24.
It is K2 Airways' only aircraft and entered service with the carrier in 2024.
Its previous flight was on June 28, according to Flightradar24 data.
The incident would be Pakistan's first fatal crash since 2020 when a Pakistan International Airlines Airbus A320 came down short of the runway in Karachi, killing 97 people.
with AP
