All flights to and from Greek airports will be canceled for 24 hours due to a general strike that will shut down public services, hospitals and schools and freeze transport across the country, authorities said Tuesday. Greece's two main labor unions called Wednesday's nationwide strike, the second in two months, to protest government efforts to reform Greece's debt-ridden and fractured pension system. «This protest will send a strong message to the government that they cannot push through changes that hurt our working rights,» said Yiannis Panagopoulos, leader of Greece's largest labor union according to The Associated Press. Air traffic controllers and civil aviation staff were to join the walkout, leaving all flights grounded. Public buses, trains and the Athens metro system will run only sporadically and hospitals will accept only emergency cases. Dentists, lawyers and teachers are also to walk off the job, while journalists will join the strike, forcing television and radio networks to cancel news bulletins and political programing. During the last general strike in mid-December, brief clashes broke out between youths and riot police as tens of thousands of strikers demonstrated through central Athens. The conservative government has pledged to overhaul the country's pension system, but its efforts have met with repeated strikes by unions that claim the reforms will lead to lower pensions and higher retirement ages.