Investigators have raised questions over training and cockpit procedures at Indonesian budget carrier Lion Air after a preliminary report into a crash last month off Bali found the captain was not at the controls at a "critical time".
The National Transportation Safety Committee said in a report that Lion Air should immediately review or reinforce a number of safety measures related to landing procedures carried out by pilots.
However, it did not say how it had arrived at the preliminary conclusions from a sample of evidence compiled from "black box" flight data and cockpit voice recordings.
All 108 passengers and crew survived when the passenger jet undershot the tourist island's main airport runway and belly-flopped into the water.
The report, released late on Tuesday, did not give an exact cause of the crash, but ruled out any major problems with the almost brand-new Boeing (BA.N) 737-800 passenger jet.
Weather reports indicated that there was a sudden loss of visibility in the area, it said, adding the second-in-command was in charge seconds before the plane crashed into the sea just before the runway.
Lion Air's co-founder Rusdi Kirana said he would respect the outcome of the investigation, but voiced dismay at the interim recommendations which were directed solely at the airline.
"If our pilots make mistakes we are not scared to admit it, but we are not happy just blaming the pilots without proof," he told Reuters.
"It is important not to give people the impression that we don't have proper procedures. We take safety seriously, we are a profitable airline and we are not going to limit our budget on training and maintenance."
The cause of the crash has potential implications for the reputation of one of the world's fastest-growing airlines, which is fighting to be removed from a European Union safety blacklist even as it buys record volumes of Airbus and Boeing jets.
Indonesia has also failed U.N. agency the International Civil Aviation Organization's standards for aircraft operations and maintenance, and as a result American regulators have imposed restrictions on them starting or increasing flights to the United States.
The preliminary report said that the 24-year-old second-in-command, who had 1,200 hours of flying experience, was in control during the descent into the airport and reported that he could not see the runway 900 feet above ground.
The captain switched off the auto-pilot and the second-in-command handed over controls to him at 150 feet - or 1 minute, 6 seconds before the crash - after saying he again could not see the runway.
One second before the crash and with 20 feet separating the aircraft and the water, the pilot commanded a "go-around" and attempted to abort the landing, but the plane hit the water.
The report recommended Lion Air "review the policy and procedures regarding the risk associated with changeover of control at critical altitudes or critical time".
It added the fast-growing airline should also "ensure the pilots are properly trained" on this subject.
The airline said standard aviation practice allowed pilots to change control at any time at the crew's discretion.
It defended its standard procedures for aborting a landing and said these had last been reviewed in March last year.
A person familiar with the matter told Reuters last month that the pilot had described how he felt the 737-800 passenger jet being "dragged" down by wind while he struggled to regain control.
The NTSC report said that the navigational aids and approach guidance facilities such as the runway lights at Bali's Ngurah Rai International Airport were all "functioning properly" at the time of the crash.
It did not address whether these facilities should include an Instrument Landing System (ILS).
Industry experts say such a feature is common at airports worldwide to help pilots keep to the right descent path. Bali does not have an ILS for planes landing from the West.
The report also did not address whether the jet may have been subject to wind shear or dangerous gusts of wind. Airport officials have told Reuters some of the airports at Asia's best known holiday spots do not have wind shear detectors.
The NTSC said it expected to release its final report within the next 12 months.
Founded by two brothers and travel entrepreneurs, Lion Air has been growing at a record pace to keep up with one of the region's star economies. Earlier this year, it signed a deal with Europe's Airbus for 234 passenger jets worth $24 billion. Two years ago, it signed a deal with Boeing for 230 planes.
At the same time, however, Indonesia has been struggling to improve its civil air safety after a string of deadly accidents.
In 2007, Lion Air was among a number of Indonesian airlines banned by the EU for lax safety standards.
The ban was progressively lifted, starting in 2009, but although it has had one fatal accident, Lion Air remains on the EU's banned list - a predicament it has dismissed as unfair.
(Reporting by Siva Govindasamy in Singapore, Janeman Latul in Jakarta and Tim Hepher in Paris; Editing by Jeremy Laurence)