A Taiwanese air force pilot was killed and another is missing after two fighter jets collided in mid-air and crashed into the sea off the south of the island on Monday, the third such incident in six months. The two F-5E fighter jets each had one pilot on board and went missing from radar around 3pm, about 1.4 nautical miles from the fishing town of Mudan in Pingtung county, air force Chief of Staff Huang Chih-wei said. They had taken off with two other F-5s from the Chihang airbase in Taitung, eastern Taiwan, at 2.30pm for a training mission, he said. “We sent out five helicopters, two naval and six coastguard vessels as well as rescue units from Taitung and Pingtung for the search,” Huang told reporters. He said the two single-seat fighter jets apparently collided in mid-air as they were about to return to the base. “The pilots of the two other jets reported seeing plane debris in mid-air and signs that the pilots had been forced to eject from their aircraft,” Huang said. One of the pilots, identified as Lo Hsiang-hua, 26, was later found unconscious at sea and confirmed dead at a hospital in Taitung, he said. Rescuers were still looking for the second pilot, identified as 28-year-old Pan Ying-chun. Huang said the air force had grounded all of its F-5 fighter jets and some other aircraft would also be grounded to undergo safety inspections. President Tsai Ing-wen expressed concern over the accident and called for rescue efforts to be stepped up. The ageing F-5 fleet was also grounded in October after one of the US-made fighter jets crashed into the Pacific Ocean during a training mission off Taitung, less than two minutes after it took off from the Chihang airbase. The pilot, identified as Captain Chu Kuan-meng , ejected into the ocean but was found unconscious and declared dead about an hour later at a nearby hospital. Another pilot was killed in November when an F-16A fighter jet crashed off the east coast of the island. Taiwan counts 15 lives lost in 2020 and rising military cost amid escalating tension with China The latest incident comes as Taiwan’s military has been on high alert amid increasing intimidation from Beijing, which claims the island as part of its territory to be brought under mainland control, by force if necessary. The People’s Liberation Army’s stepped up activities include repeatedly sending warplanes into the self-ruled island’s air defence identification zone (ADIZ). Earlier on Monday, Taiwan’s defence ministry said two PLA warplanes had entered the island’s southwest ADIZ and it had scrambled fighter jets, issued radio warnings and deployed its missile systems to monitor their activities. Taiwan started assembling F-5E/F fighter jets on the island in 1973, with all necessary technologies and key engines provided by US-based Northrop Corporation. At one time the Taiwanese air force had 242 single-seated F-5Es and 66 twin-seated F-5Fs. With the introduction of 150 F-16s from the US, 60 Mirage 2000-5s from France and 130 indigenous F-CK-1s in the mid-to-late 1990s, the F-5 series was downgraded to the air force’s second line of fighters and they have now been mostly withdrawn from service.