Airline travelers were urged yesterday not to panic as the government assured people that airport security in Greece was adequate following the uncovering of an alleged plot in Great Britain to blow up airplanes with liquid explosives. Hundreds of passengers were delayed at Athens International Airport as all Olympic Airlines flights to Britain were suspended following a heightened security alert. British Airways and easyJet also canceled flights as British authorities said they averted «mass murder» in the skies by thwarting an alleged plot to blow up passenger planes bound for the United States. A British Airways flight which left for London yesterday morning was forced to return to Athens because of the alert. An Olympic Airlines flight which departed Athens for Heathrow airport at 6.15 p.m. was the first flight of the day to leave for Britain. A British Airways flight to Gatwick Airport also left soon afterward. Flights from the UK to Greece were also severely delayed. The arrests of 21 people triggered in Britain worldwide security alerts. Passengers were forced to repack their hand luggage and only carry essential belongings through security in clear plastic bags. However, government sources said that Greece has not been asked to take any additional security measures, adding that tight checks are already in place at Greek airports. «There is no cause for concern in Greece,» said Transport Minister Michalis Liapis. «Greece has won the reputation of being a safe country and the successful hosting of the Olympic Games proved it,» said Tourism Minister Fanni Palli-Petralia.