Air India said on Thursday it is investigating whether its crew followed all compliance procedures when a Boeing 787 took off from London with a potential fuel-switch defect, only to be grounded later in India.

Reuters first reported the airline’s investigation, following its earlier coverage that Britain’s aviation authority had privately requested details of all maintenance actions prior to the flight. The U.K. regulator has given Air India one week to provide a full response, warning of possible regulatory action affecting the airline and its fleet of 33 Dreamliners.

Authorities said pilots in London noticed the fuel control switch did not stay latched in the “run” position on two attempts, but was stable on a third. Despite this, the crew flew to India, where the pilot reported a potential defect on landing, prompting the aircraft to be grounded for checks.

In a statement, Air India said it would follow its safety investigation protocol and take appropriate action, but did not elaborate.

A source told Reuters that the airline’s probe would examine why the crew did not report the issue in London and why it was flagged only upon landing in India. India’s civil aviation authority did not immediately comment.

Fuel switches, which control the flow of jet fuel to engines, were central to last year’s Air India Dreamliner crash in Gujarat, which killed 260 people and led to tighter scrutiny of the airline. Air India and Indian authorities have said no problems were found with fuel switches on the Dreamliner fleet after Sunday’s incident.

The U.K. watchdog has requested a comprehensive root-cause analysis and a preventive action plan to prevent similar issues across Air India’s 787 fleet.

“The safety of our passengers and crew remains Air India’s highest priority,” the airline said.