El Al operate this route from London.
But as of early Friday morning, flights were not taking off for Israel.
British Airways is not currently operating flights to Tel Aviv.
UK citizens in the Middle East were also put on alert on Friday.
They were urged to follow the latest advice from the Foreign Office as Tehran sought to hit back with drone attacks.
The “dangerous moment” situation was expected to flare up rapidly with fast-moving developments.
There were already reports of some 100 drones sent by Tehran being intercepted by Israel’s air force over Saudi Arabia.
Amid fears of a widespread war in the Middle East, Sir Keir Starmer “urged all parties to step back” after Israeli strikes targeting Iran’s nuclear programme.
He added: “The reports of these strikes are concerning and we urge all parties to step back and reduce tensions urgently. Escalation serves no-one in the region.”
“Stability in the Middle East must be the priority and we are engaging partners to de-escalate. Now is the time for restraint, calm and a return to diplomacy.”
The attack appeared to be the most significant Iran has faced since its war with Iraq in the 1980s.
Iran had launched about 100 drones towards Israeli territory in retaliation, which Israel is working to intercept, Israeli military spokesman Brigadier General Effie Defrin said.
Iranian media and witnesses reported explosions including at the country’s main uranium enrichment facility at Natanz, while Israel declared a state of emergency in anticipation of retaliatory missile and drone strikes.
The International Atomic Energy Agency said on Friday there was no increase in radiation levels at the Natanz nuclear site, citing information given to them by Iranian authorities.
Iran’s elite Revolutionary Guards corps said its top commander, Hossein Salami, was killed and state media reported the unit’s headquarters in Tehran had been hit. Several children had been killed in a strike on a residential area in the capital, it said.
Read More
“We are at a decisive moment in Israel’s history,” Israeli Prime Minister Benjamin Netanyahu said in a recorded video message.
“Moments ago Israel launched Operation Rising Lion, a targeted military operation to roll back the Iranian threat to Israel’s very survival. This operation will continue for as many days as it takes to remove this threat.”
Defrin said 200 Israeli fighter jets took part in the strikes, hitting more than 100 targets in Iran.
Israel could confirm that the chief of staff of the Iranian Armed Forces, the commander of the Revolutionary Guards and the commander of Iran’s Emergency Command were all killed in the strikes across Iran, he told an online briefing.
Iran’s Supreme Leader Ayatollah Ali Khamenei said in a statement that Israel had “unleashed its wicked and bloody” hand in a crime against Iran and that it would receive “a bitter fate for itself”.
British Foreign Secretary David Lammy stressed: “This is a dangerous moment & I urge all parties to show restraint.”
Airlines cleared out of the airspace over Israel, Iran and Iraq and Jordan on Friday after the Israelis strikes, Flightradar24 data showed, with carriers scrambling to divert and cancel flights to keep passengers and crew safe.
Iran closed its airspace and Tel Aviv’s Ben Gurion Airport was closed until further notice.
German airline Lufthansa on Friday said it had suspended all flights to and from Tehran following widescale strikes by Israel against Iran.