A memorial service has been held in Co Mayo to mark the second anniversary of the Rescue 116 Coast Guard Helicopter crash.

Four crew members lost their lives when the Sikorsky S-92 aircraft crashed into Blackrock Island, in the early hours of 14 March 2017.

The bodies of Captain Dara Fitzpatrick and Captain Mark Duffy were recovered in the days following the tragedy.

The remains of their colleagues, winch operator, Paul Ormsby and winch man, Ciarán Smith, remain lost at sea.

Relatives of the deceased gathered for an anniversary mass at St Brendan's Church near Eachléim this evening.

Two years on, investigations are continuing and there are ongoing efforts to implement a number of recommendations made after the crash.

The Department of Transport says work is continuing to implement recommendations from a review into the management of search and rescue aviation operations.

The review was published last September, after an investigation into the crash said the oversight of such operations needed to be examined. 

It made a total of 12 recommendations and gave timeframes for their implementation. 

But nearly six months later, just one of the recommendations has been implemented in full.

Work is continuing to progress two other ‘short term’ actions.

A department spokesperson said the Irish Aviation Authority had reviewed the safety management system of CHC - the company with the contract to operate Coast Guard helicopter services. This found the process in place were appropriate.

The IAA is continuing to work towards enhancing its oversight role for air-based SAR activities. It has also been involved in discussions with the Coast Guard to ensure there is consistency about how regulations are applied. 

The department says a review of the National Search and Rescue Framework has been launched to encompass a number of other recommendations contained in last September’s report.

The former CEO of the UK Maritime and Coastguard Agency is chairing a review group to progress those ‘medium-term’ recommendations.

As well as looking at the issues raised in relation to air based operations, the process is also examining advice from a separate inquiry into the death of Coast Guard volunteer Caitríona Lucas in Kilkee, Co Clare in 2016. 

The group is expected to finalise its deliberations during the summer. 

The department says this work is being carried out with a view to revising the guidelines for search and rescue operations, to ensure all recommendations are fully implemented.

Meanwhile, CHC has told RTÉ News that it has acted on a number of recommendations issued by the Department of Transport's Air Accident Investigation Unit.

An external review of the company's safety management system has been carried out and a revised route guide has been submitted to the Irish Aviation Authority.

In addition, all life jackets issued to Coast Guard personnel have been updated by the manufacturer and returned to CHC. This followed concerns over the manner in which safety beacons on the jackets were activated.

Earlier this month, the Air Accident Investigation Unit said it work on its final report was at an "advanced stage".

The AAIU said that rather than releasing a further interim statement on its inquiry to mark today's anniversary, it was instead focused on the completion of the overall report.

While a progress update would usually be provided in relation to ongoing investigations once a year, the AAIU said this would detract from the work of finalising the report into the causes of the crash.

All aspects of the fatal flight are being examined, including the initial tasking of the crew on the night in question.

It is thought the decision to dispatch the helicopter to provide "top cover" to another crew on the night of 13 March 2017 will be probed in detail.

A second investigation, led by gardaí, is also progressing. It has been described as a "complex process".

Detectives have been carrying out interviews, reviewing evidence and have logged each and every piece of helicopter debris that was recovered from the water in the months following the accident.

Their work is linked to the Health and Safety Authority probe into the tragedy.

When that inquiry is completed, a file will be sent to the Director of Public Prosecutions. This will ultimately determine whether criminal charges are brought in relation to the crash.

The inquests into the deaths of four crew members will not proceed until both investigations have concluded.