the work of Cardinals von Faulhaber and Pacelli, it condemns breaches of the 1933 Reichskonkordat agreement signed between the Nazi government and the Catholic Church, and criticises Nazism's views on race and other matters incompatible with Catholicism. March 18 – New London School explosion: In the worst school disaster in American history in terms of lives lost, the New London School in New London, Texas, suffers a catastrophic natural gas explosion, killing in excess of 295 students and teachers. Mother Frances Hospital opens in Tyler, Texas, a day ahead of schedule, in response to the explosion. March 19 – The encyclical Divini Redemptoris of Pope Pius XI, critical of communism, is published. March 21 – Ponce massacre: A police squad, acting under orders from Governor of Puerto Rico Blanton Winship, opens fire on peaceful demonstrators protesting at the arrest of Puerto Rican Nationalist Party leader Pedro Albizu Campos, killing 17 people and injuring over 200. April April 1 Aden becomes a British crown colony. The Bombing of Jaén is carried out in Spain, by the Condor Legion of the Nazi German Luftwaffe. April 9 – The Kamikaze arrives at Croydon Airport in London; it is the first Japanese-built aircraft to fly to Europe. April 12 – Frank Whittle ground-tests the world's first jet engine designed to power an aircraft, at Rugby, England. April 20 – A fire in an elementary school in Kilingi-Nõmme, Estonia, kills 17 students and injures 50. April 26 – Spanish Civil War: The Bombing of Guernica is carried out in Spain, by the Condor Legion of the Nazi German Luftwaffe, in support of the Francoists. Three-quarters of the town is destroyed and hundreds killed. May May 6 – Hindenburg disaster: In the United States, the German airship Hindenburg bursts into flame when mooring to a mast in Lakehurst, New Jersey. Of the 36 passengers and 61 crew on board, 13 passengers and 22 crew die, as well as one member of the ground crew. May 7 – Spanish Civil War: The German Condor Legion Fighter Group, equipped with Heinkel He 51 biplanes, arrives in Spain to assist Francisco Franco's forces. May 8 – Wydad Athletic Club (WAC)(Arabic: نادي الوداد الرياضي; Berber: Wydad Dar al-Beida; commonly: Wydad al ouma) is established in Casablanca, Morocco; it will be best known for its Casablanca Association football team. May 12 – George VI and Elizabeth are crowned King and Queen