An Iranian commercial plane crashed in a mountainous region of southern Iran on Sunday morning, killing all 65 people on board, a tragic consequences of Iran's rapidly aging fleet of commercial aircraft according to the Associated Press.

The plane was an Aseman Airlines ATR-72, a twin-engine turboprop used for short-distance regional flying. It went down near its destination of the southern Iranian city of Yasuj, some 780 kilometers (485 miles) south of the Iranian capital, Tehran.

Aseman Airlines spokesman Mohammad Taghi Tabatabai told state TV that all passengers and crew aboard Flight No. EP3704 were killed in the crash.

"After searching the area, we learned that unfortunately ... our dear passengers had lost their lives," Tabatabai said. "This plane had 60 passengers, 59 adults and one child, as well as a pilot, a co-pilot, two flight attendants and two air marshals on board."

Heavy fog prevented rescue helicopters from reaching the crash site in the Zagros Mountains, state TV reported. Tabatabai said the plane crashed into Mount Dena, which is about 4,400 meters (14,435 feet) tall.

The airline specializes in flights to remote airfields across the country. It also flies internationally. It is Iran's third-largest airline by fleet size, behind state carrier Iran Air and privately owned Mahan Air.

Aseman has a fleet of 29 aircraft, including six ATR aircraft, per the AP. The ATR-72 that crashed Sunday had been built in 1993, Aseman Airlines CEO Ali Abedzadeh said. The plane left Tehran at 0433 GMT and gave its last signal at 0555 GMT. At the time the last signal was issued, the flight was at 16,975 feet and was descending, FlightRadar24 said.

Iran Aseman Airlines flight #EP3704 (Tehran-Yasuj) has crashed.



The aircraft involved is a 24 year old ATR 72. Registration EP-ATS. MSN 391.



According to our logs flight took off at 04:33 UTC. Last signal was received at 05:55 UTC when flight was at 16,975 feet and descending. pic.twitter.com/bn2AZ9gq7d — Flightradar24 (@flightradar24) February 18, 2018

Aseman Airlines has suffered other major crashes with fatalities. In October 1994, a twin-propeller Fokker F-28 1000 commuter plane flown by the airline crashed near Natanz, 290 kilometers (180 miles) south of Tehran, also killing 65 people on board. An Aseman Airlines chartered flight in August 2008, flown by an Itek Air Boeing 737, crashed in Kyrgyzstan, killing 74 people.

Following the 2015 landmark nuclear deal with world powers, Iran signed deals with both Airbus and Boeing to buy scores of passenger planes worth tens of billions of dollars. U.S. politicians have expressed concern about the airplane sales to Iran. President Donald Trump remains skeptical of the atomic accord overall and has refused to re-certify it, putting the deal in question.

Decades of international sanctions have left Iran's airline industry with an aging fleet. Aseman Airlines, which is owned by an Iranian pension fund and is considered semi-private, isn't allowed to fly in the European Union because of safety concerns.