It was tasked with air transportation, airdrop and electronic reconnaissance. Some 25 members of the unit were killed, among them 17 pilots and co-pilots, and three aircraft were lost. Other ROC involvement in Vietnam included a secret listening station, special reconnaissance and raiding squads, military advisers and civilian airline operations (which cost a further two aircraft due to Vietnamese individually operated AA missiles). From 1979 to 1990, the ROCAF engaged in a classified military aid program in the Yemen Arab Republic, known as the Great Desert Program (). The program started after American President Jimmy Carter rushed 14 F-5s to the Yemeni Air Force who had no pilots or ground crew trained to operate the type or even any Western aircraft (they previously operated MiG-15s). The Americans and the Saudis (who were bankrolling the Yemen Arab Republic's military) requested military aid from Taiwan who provided 80 F-5 pilots, ground crews, early warning radars, and anti-aircraft missile batteries. All told more than a thousand ROCAF personnel were deployed to Yemen. The opposing Air Force of South Yemen was made up of Cuban pilots and maintainers with some Soviet advisors and pilots as well. The ROCAF force were actively involved in combat with the Cubans/Soviets and for all intents and purposes constitutes the Yemen Arab Republic's Air Force during this time. Taiwanese pilots scored a number of kills in Yemen. The program ended in 1990 when Saudi Arabia withdrew its diplomatic recognition of Taiwan. From democratization The transition to democracy was difficult for the ROCAF and the Taiwanese military overall. During the martial law period the military was a pillar of totalitarianism and dictatorship and for this reason was mistrusted by the Taiwanese public. Spending and personnel levels fell from the beginning of democratization until the Tsai Ing-wen administration began increasing military spending in 2016. Efforts have been made to enhance the status of the military in the eyes of the public. The ROCAF has been under increasing financial and physical pressure due to an increase in PLA Air Force intrusions into Taiwanese airspace and subsequent interception by Taiwanese fighters. On November 29, 2020, the ROCAF celebrated its 100th birthday. On the event of their 100th birthday Taiwanese President Tsai Ing-wen commended the "loyal and fearless heroes" of the Air Force and added that "The sound of the roaring engine is our guardian, the voice of democracy and freedom." Humanitarian operations The