US President trump had previously threatened to attack 52 targets in Iran. In response, Iranian President Rouhani tweeted in the early morning of the 7th: "those who mention the number of 52 should also remember 290# Iran flight 655 #. Never threaten Iran. "
According to the Washington Post, Trump's reference to the number '52' highlights the past grievances between the United States and Iraq. In 1979, after the Islamic revolution in Iran, the U.S. embassy was occupied and 52 U.S. diplomats and civilians were taken hostage.
Rouhani's' 290 'refers to an air crash more than 30 years ago. In July 1988, Iran Airlines flight 665 was shot down by the US military in the Persian Gulf, killing all 290 people on board. The US government explained that at that time, the aircraft did not respond to military and civil radio signals, and was mistaken by the US side as a fighter on mission. The Iranian government believes that during the Iran Iraq war, the United States expressed its support for Iraq by shooting down an Iranian airliner. Source: Beijing News