The UK aviation regulator has requested an explanation from Air India regarding a Boeing plane's fuel switch issue, which was cleared to fly despite the potential safety concerns. The incident occurred when a Dreamliner plane, arriving from London, was grounded in India for safety checks immediately after landing. The crew noticed a fuel control switch malfunction during engine start, causing alarm as it was linked to a previous Air India crash. The crash, the deadliest in decades, resulted in 241 fatalities. The regulator's letter demanded a detailed account of maintenance actions, a root-cause analysis, and a preventive plan to ensure the issue doesn't recur. This comes after Air India claimed no issues were found during a re-inspection, but the regulator warned of potential regulatory action if a complete response isn't provided within a week. Boeing is cooperating with the investigation, and an internal memo confirms no issues were found with fuel switches on all 33 Boeing 787s. However, a preliminary report suggests the switches flipped simultaneously, causing engine starvation, leaving questions about the exact cause.