The propeller plane pitched into a dive over a city. The pilot released a bomb as the plane leveled off, and the ordnance ripped into an urban neighborhood, spraying debris over several buildings.

The scene, captured in a recent viral video, is said to have occurred over Marawi, a city of 200,000 people in the southern Philippines where a fierce battle has been waged since last month between government security forces and militants aligned with the Islamic State. Most residents have fled the city, and bombs have been dropped regularly onto areas held by the militants.

At the center of the fight has been the OV-10 Bronco, a Vietnam War-era plane that the Philippines has deployed along with jets like the FA-50 Fighting Eagle, a light combat fighter that the government in Manila has bought in waves from South Korea.

The OV-10 has been photographed flying in formations over the city in between bombing runs. Initially conceived in the 1960s in the United States, it offered U.S. forces in Vietnam a simple, rugged plane that could carry out close-air support for American troops on the ground and take off from short runways. It remained in service in the U.S. military until the 1990s, undertaking operations in the Persian Gulf War.

The Philippines acquired more than 20 used OV-10s from the United States in the early 1990s and more from Thailand in 2004. The turboprop plane provided a way for the country to attack enemies from the air while on a tight budget.

But the plane’s use has come into question as it has aged, especially following crashes in 2010 and 2013. The military temporarily grounded all eight of its remaining OV-10s in 2013 but defended their continued use, noting that they had received numerous upgrades, according to a report by the Philippine Star newspaper.

The plane began carrying satellite-guided bombs supplied by the United States in 2012, according to another Philippine news report at the time, but it only does so some of the time. The country has signaled a desire this year to begin replacing the remaining Ov-10s by opening bidding for new close-air support planes.

A 2012 report by the conservative Heritage Foundation noted that the Philippine air force was one of the strongest in the region, with nearly 50 fighter jets in addition to the OV-10s in the 1980s. The numbers dwindled over time, and Philippine officials ordered the remaining Vietnam War-era F-5 fighters decommissioned in 2005.

The U.S. military has experimented with light-attack planes, including the OV-10, in recent years as a low-cost way of carrying out airstrikes on insurgencies like the Islamic State. Most strikingly, it deployed two highly upgraded OV-10s on loan from NASA to Iraq in 2015, carrying out airstrikes and reconnaissance missions.

The U.S. Air Force is planning a “live-fly experiment” from July 31 through Aug. 30 at Holloman Air Force Base in New Mexico, during which companies will demonstrate the abilities of their light-attack aircraft, said Ann Stefanek, a service spokeswoman. Gen. David L. Goldfein, the service’s top officer, has said that he is interested in aircraft that can be used “off the shelf,” without much time and money spent on researching how they can be incorporated.