NEW DELHI: A Mumbai-bound Air India's Boeing 777 aircraft returned to the national capital due to a right engine issue on Monday morning, according to sources.

The plane, carrying around 335 people, was airborne for nearly an hour before returning to Delhi. The aircraft made an emergency landing, they added.

"The crew operating flight AI887 from Delhi to Mumbai on 22 December decided to return to Delhi shortly after take-off due to a technical issue as per standard operating procedure," Air India said in a statement.

The aircraft landed safely at Delhi and the passengers and crew have disembarked, the airline said and regretted the inconvenience caused due to this unforeseen situation.

A source at the Directorate General of Civil Aviation (DGCA) said the plane made an air turn back as during flap retraction after take-off, the flight crew observed low engine oil pressure on the right hand engine.

The engine oil pressure dropped to zero, and the inspection is in progress, the source said.

The source also noted that review of previous records does not indicate any abnormality in oil consumption.

According to the airline, the plane is undergoing the necessary checks and alternative arrangements have been made to fly the passengers to their destination.

The flight AI887 was being operated with a Boeing 777-300 ER aircraft and was airborne for about an hour after taking off around 6.30 am, as per information available on flight tracking website Flightradar24.com.