New Delhi, Apr 12 (IANS): Budget carrier IndiGo's Delhi-Mumbai flight had to perform a mid-air "turn back" manoeuvre due to excessive vibration from the aircraft's engine number two, industry insiders privy to the development said on Friday.

However, an airline official said that the aircraft had suffered a bird hit en-route from Delhi to Mumbai on Wednesday.

The A320 NEO aircraft operated by IndiGo has faced a series of problems earlier with engine vibration being one of them.

Industry sources said that at least 15 cases of mid-air engine problems have been reported in the A320 NEOs operated by IndiGo and GoAir since January.

Engine vibration resulting in mid-air turn backs has emerged as the most common and serious safety issue with the P&W engine powered NEOs of late.

The country's aviation regulator is said to be examining the incident.

Wednesday's incident comes days after the budget passenger carrier's Delhi-Istanbul flight had to be diverted to Kuwait.

The airline that time had said that an engine snag had hit its A320 NEO aircraft which was en-route from Delhi to Istanbul.