An Iranian passenger plane with 144 people on board has skidded off a runway and on to a road with its wheels still retracted. The incident took place in the Iranian city of Mahshahr. Caspian Airlines Flight 6936 departed from the capital city, Tehran, early on Monday and was set to land at Mahshahr Airport, in the country's south-west. The plane instead skidded on to Mahshahr-e-Ahwaz motorway, Iranian news agency Fars reported, blocking traffic and pedestrians on either side of the road. Passengers, apparently in shock, calmly exited the aircraft with their carry-on baggage out of a door near the cockpit and another over the plane’s wing, video from Iran’s Civil Aviation Network News showed. A flight attendant shouted at passengers to calmly walk away as another crew member joined her on the wing. “We crashed. We crashed but we are unhurt,” a male passenger said in Farsi in the video. “My hand is shaking.” Caspian Airlines is based in Tehran. Its last major accident was in 2009, when a commercial flight crashed outside the city of Qazvin in north-western Iran. All 153 passengers and 15 crew members on board died, making it one of the deadliest aviation accidents in the country's history. Provincial airport director Mohammad Reza Rezanian said all of the passengers had been safely taken off the plane, which had been flying a route from the Iranian capital, Tehran, 610 kilometres north-east of Mahshahr. The plane carried 136 passengers and eight crew members, the authorities said. Iranian state television said the plane involved in Monday’s crash-landing came in harder than usual and lost its landing gear as it hit the tarmac. No landing gear could be seen in pictures of the plane after the crash, but it was not immediately clear if it failed to deploy or somehow collapsed as the jet hit the runway at about 7.35am local time. The accident is being investigated, officials said. The McDonnell Douglas MD-83, a single-aisle plane introduced in the mid-1980s, has largely been phased out of commercial air travel in the West. American Airlines retired the last of its MD-80 fleet in September. The plane involved in Monday’s crash-landing in Iran, registered as EP-CPZ, was more than 25 years old. It flew for airlines in France, Canada, the US, Colombia, Burkina Faso and Ukraine before being registered to Caspian Airlines in August 2012. The incident comes as Iran is still coping with the aftermath of the accidental shooting down of a Ukrainian airliner over Tehran. The plane was shot down earlier this month amid heightened tensions with the United States, killing all 176 people aboard. Maintenance information regarding the US-built MD-83 that crashed Monday was not immediately available. However, Iran has struggled to obtain parts for its aging fleet of airliners amid US sanctions.