Egypt's Civil Aviation Ministry announced on Wednesday that it has instructed Egyptian airlines to avoid Iranian airspace for a three-hour period on Thursday. This directive followed a notification from Tehran about scheduled military drills.

The advisory comes amid heightened regional tensions after the assassination of a Hamas leader in Tehran last week.

Egypt stated that the warning was part of a notice issued by Iran to all commercial airlines.

The restriction on Iranian airspace will be in effect from 4:30am to 7:30am on Thursday, with a similar warning also in place for three hours earlier on Wednesday, according to the Egyptian ministry.

Moreover, Britain has also asked its airlines to avoid Lebanese airspace amid growing fears of a possible broader conflict in the region. Britain's advisory to its airlines to avoid Lebanon's airspace came hours after Egypt instructed all of its airlines to avoid Iran's airspace for three hours in the early morning on Thursday.

Many airlines globally are revising their schedules to avoid Iranian and Lebanese airspace while also calling off flights to Israel and Lebanon.

Flights through conflict zones became a prominent industry safety issue a decade ago after Malaysia Airlines flight MH17 was shot down over Ukraine, killing all 298 people on board. 

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U.S.-based United Airlines said on Wednesday its flights to Tel Aviv, which were paused on July 31 due to security concerns, remained suspended. "We continue to closely monitor the situation and will focus on the safety of our customers and crews as we decide when to resume service," the airline said.

Its rival Delta Air Lines has paused its flights between New York and Tel Aviv through Aug. 31.

British carriers are not flying to Lebanon currently, according to flight tracking website Flightradar24.

Singapore Airlines stopped flying through Iranian airspace last Friday and is using alternative routes, saying safety is its top priority.

Similarly, Egyptian airlines have already been avoiding Iran's airspace. The new directive applies to all Egyptian carriers, including charter operators and other smaller airlines, said Mark Zee, founder of OPSGROUP - a membership-based organization that shares flight-risk information.

Egypt's NOTAM, a safety notice provided to pilots, said the instruction would be in effect from 0100 to 0400 GMT on Thursday.

"All Egyptian carriers shall avoid overflying Tehran (Flight Information Region). No flight plan will be accepted overflying such territory," the notice said, referring to the three-hour period specified.

Egypt's civil aviation ministry later confirmed on Wednesday the notice was intended to reduce flight safety risks in light of a notification it received from Iranian authorities.