Iran reopened its airspace after a near-five-hour closure amid concerns about possible military action between the U.S. and Iran that forced airlines to cancel, reroute or delay some flights.

Iran closed its airspace to all flights except international ones to and from Iran with official permission at 5:15 p.m. ET (2215 GMT) on Wednesday, according to a notice on the U.S. Federal Aviation Administration website.

The notice was removed shortly before 10 p.m. ET, or 0300 GMT, according to tracking service Flightradar24, which showed five flights from Iranian carriers Mahan Air, Yazd Airways and AVA Airlines were among the first to resume over the country.

At a similar time last week to the airspace closure there had been dozens of planes in the air over Iran, Flightradar24 said.

The temporary closure came as President Donald Trump has been weighing a response to the situation in Iran, which is seeing its biggest anti-government protests in years.

The United States was withdrawing some personnel from bases in the Middle East, a U.S. official said on Wednesday, after a senior Iranian official said Tehran had warned neighbors it would hit American bases if Washington strikes.

Missile and drone barrages in a growing number of conflict zones represent a high risk to airline traffic.

India’s largest airline, IndiGo (INGL.NS), said some of its international flights would be impacted by Iran’s sudden airspace closure. Air India said its flights were using alternative routes that could result in delays or cancellations.

A flight by Russia’s Aeroflot (AFLT.MM), bound for Tehran returned to Moscow after the closure, according to Flightradar24 data.

Earlier on Wednesday, Germany issued a new directive cautioning the country’s airlines from entering Iranian airspace, shortly after Lufthansa (LHAG.DE), rejigged its flight operations across the Middle East amid escalating tensions in the region.

The United States already prohibits all U.S. commercial flights from overflying Iran and there are no direct flights between the countries.

Airline operators like flydubai and Turkish Airlines have canceled multiple flights to Iran in the past week.

“Several airlines have already reduced or suspended services, and most carriers are avoiding Iranian airspace,” said Safe Airspace, a website run by OPSGROUP, a membership-based organisation that shares flight risk information. “The situation may signal further security or military activity, including the risk of missile launches or heightened air defence, increasing the risk of misidentification of civil traffic.”

A Ukraine International Airlines jet was downed by Iran’s military in 2020, killing all 176 passengers and crew.

Lufthansa said on Wednesday that it would bypass Iranian and Iraqi airspace until further notice while it would only operate day flights to Tel Aviv and Amman from Wednesday until Monday next week so that crew would not have to stay overnight. Some flights could also be canceled as a result of these actions, it added in a statement.

Italian carrier ITA Airways, in which Lufthansa Group is now a major shareholder, said that it would similarly suspend night flights to Tel Aviv until Tuesday next week.