United Arab Emirates President and Emir of Abu Dhabi Sheikh Khalifa bin Zayed al-Nahyan died Friday, the country's Emirates News Agency said. He was 73, according to The Associated Press. Khalifa became the Gulf state's president in 2004. He underwent an operation for a stroke in 2014. His brother Mohamed bin Zayed al-Nahyan has wielded power in recent years. The Ministry of Presidential Affairs said the country will observe a 40-day national mourning with the flag flown at half-mast, the agency said.