The call from the Department for Transport comes amid fears a Ukrainian passenger jet, which crashed shortly after taking off from Tehran on Wednesday morning (8 January), was brought down by an Iranian missile.

Balpa said it expected all UK airlines to follow the two Notice to Airmen advisories issued in the early hours of this morning (10 January).

General secretary Brian Strutton said the union urged the government to maintain its position "until and unless there is a significant improvement in the security situation in the Middle East."

"The precautionary principal should be used in all decision-making in aviation, and that certainly applies here.

The Foreign Office has banned all travel to Iran due to "heightened tensions in the region".

Prime minister Boris Johnson echoed statements from Canadian president Justin Trudeau and US president Donald Trump, saying there was now a "body of information" suggesting Ukrainian International Airlines (UIA) flight PS752 "was shot down by an Iranian surface to air missile".

All 176 people, 167 passengers and nine crew, died when the plane burst into flames and crashed on the outskirts of Tehran. Onboard were four British nationals.

All three leaders have through stressed the incident "may well have been unintentional".

The crash occurred just hours after Iran launched retaliatory missile strikes on two Iraqi military bases housing US and coalition personnel following the death of top general Qasem Solemeini, who was killed in a US airstrike on Friday (3 January).

Balpa added: "The increasing evidence that Flight PS752 may have been shot down is extremely concerning. Peaceful civil aviation should never find itself involved in armed conflict. Our thoughts are with the families of the passengers and crew who fell victim to this tragedy.”