A Mumbai-Delhi Air India flight (886) faced an unexpected delay of four hours on Wednesday after developing a technical snag while it was about to take off. 
Aviation experts raised concerns, stating that a flight does not go on the runway before the clearance from the engineers. 

“This generally does not happen as the aircraft is always cleared by the engineers first before the pilot gets a pushback and taxi clearance from the Air Traffic Control (ATC). Here, two points need to be investigated: Was the aircraft actually thoroughly checked by the engineers? And did the aircraft develop a technical snag after the engineers cleared it?” A senior flight instructor and staffer told mid-day.