DUBLIN—The Irish airline Ryanair on Monday urged Belarus to guarantee that there would be no repeat of the forced landing of one of its flights last May, and said airlines should not fly over Belarus without such a guarantee. The plane was overflying Belarus on its way from Athens to Vilnius when Belarus controllers ordered it to land in Minsk, citing a bomb threat. Once it was on the ground, a Belarusian dissident journalist on board the plane was arrested along with his female companion. Western powers responded with a wave of new sanctions and the United States this month charged four Belarus officials with aircraft piracy. A United Nations report published on Jan. 17 found that the reported bomb threat had been invented, without identifying the source of the hoax. It said Belarus had withheld crucial information from the U.N. fact-finding team. Ryanair Group boss Michael O’Leary said the …