An issue with one of the engines reportedly forced an Air India plane bound for Maharashtra's Mumbai to return to Delhi on Monday morning after being airborne for about an hour.

The aircraft, a Boeing 777, was carrying around 355 people, according to the PTI news agency.

"The crew operating flight AI887 from Delhi to Mumbai on 22 December decided to return to Delhi shortly after takeoff due to a technical issue as per standard operating procedure," an Air India spokesperson said in a statement, without detailing what the technical issue was.

'Engine oil pressure drops to zero'

The plane made an air turn back, as during flap retraction after takeoff, the flight crew observed low engine oil pressure on the right-hand engine, PTI news reported first, quoting a source at the Directorate General of Civil Aviation (DGCA) as saying.

The engine oil pressure dropped to zero, and the inspection is in progress, the above-mentioned source said but also added that a review of previous records does not indicate any abnormality in oil consumption.

The Directorate General ​of Civil Aviation (DGCA) later issued a ‍statement on the incident and confirmed the above, adding that the crew shut down ​the ⁠engine before the ⁠aircraft landed safely in ‌Delhi, Reuters reported.

What Zero Oil Pressure Means

Engine oil pressure dropping to zero signals a complete loss of lubrication in the turbine engine, which relies on high-pressure oil to reduce friction between thousands of high-speed rotating parts like bearings, shafts, and gears operating at temperatures exceeding 1,000°C.

Without oil, metal components seize almost immediately due to extreme heat and mechanical stress, potentially leading to engine disintegration, fire, or uncontained failure where debris punctures the nacelle or fuselage.

Pilots are trained to treat zero pressure as an engine-out scenario, relying on the remaining powerplant for flight. Boeing 777s are certified for extended twin-engine operations over water (ETOPS) with one engine inoperative.

The critical role of engine oil pressure

Oil pressure is vital for engine health, performing multiple life-sustaining functions beyond lubrication: it cools critical components by absorbing and dissipating heat, seals gaps to maintain compression efficiency, and cleans debris through filtration.

Continuous monitoring ensures early detection of issues like leaks, pump failures, or blockages.

A zero reading mandates shutdown to prevent secondary failures like turbine blade liberation, which could endanger the aircraft. This incident shows the rigorous aviation safety protocols, where conservative pilot decisions prioritise lives over schedules.

Source: Reuters/Hindustan Times/India Today/PTI