MELBOURNE (Reuters) - Australia's Qantas Airways Ltd (QAN.AX: Quote, Profile, Research) said passengers should have confidence in the airline, as regulators launched a safety investigation after three of its planes were forced to make emergency landings.

The Civil Aviation Safety Authority (CASA) is reviewing the airline's operations after a Qantas flight bound for Manila carrying 200 passengers was forced to turn back to Sydney on Saturday when the pilot discovered a hydraulic fluid leak.

Part of the undercarriage blew off another Qantas flight from Hong Kong to Melbourne eight days earlier, forcing an unscheduled landing in Manila, and a domestic flight returned to its departure city on Tuesday after a wheel bay door failed to close.

Qantas Chief Executive Geoff Dixon hands over charge of the airline in November to Irishman Alan Joyce after a string of belt tightenings because of high fuel costs.

"CASA says it has no evidence to suggest that safety standards at Qantas have fallen," Executive General Manager of Qantas Engineering David Cox said in a statement.

"We have no issue with this latest review," he said.

Qantas, which has 225 aircraft and a reputation stretching back almost 90 years as one of the safest airlines, has never had a fatal accident.

(Reporting by Miranda Maxwell)