Iran is closing its airspace to all flights, except for international flights to and from the Islamic Republic that have special permission, Reuters reported, citing a statement published on the website of the US Federal Aviation Administration.
The ban takes effect at 00:30 GMT and is due to last for two hours, but could be extended, the statement said.
Tehran warned its neighbors on Tuesday that it would strike US military bases on their territory if Washington attacks Iran.
India's largest airline "IndiGo" said some of its international flights would be affected by the sudden closure of Iranian airspace. A Russian airline Aeroflot flight bound for Tehran has returned to Moscow after being grounded, according to data from the Flightradar24 website.
German airline Lufthansa said on Wednesday it would avoid Iranian and Iraqi airspace until further notice. The airline added that from Wednesday to Monday next week it would only operate daytime flights to Tel Aviv and Amman. German authorities issued a warning to German airlines last night not to enter Iranian airspace.
Italian carrier ITA Airlines (ITA) also said it would suspend nighttime flights to Tel Aviv until Tuesday next week.
The United States has banned American passenger planes from flying over Iran. Airlines such as "flyDubai" and "Turkish Airlines" have also canceled a number of flights to the Islamic Republic.
Meanwhile, Britain advised its citizens not to travel to Israel unless they have a compelling reason. Earlier, the British government issued a similar warning, which only applied to certain parts of Israel. "There is an increased risk of regional tensions. Escalation could lead to travel disruptions and other unintended consequences," says a recommendation published on the British Foreign Office website.