Updated 19:19

The RNLI have said there's still no sign of the missing Rescue 116 crewmen Ciarán Smith and Paul Ormsby, after one of the largest sea searches ever undertaken in the history of the state.

Up to 120 fishing vessels from Arranmore in Donegal to Achill Island joined the search for Paul Ormbsby and Ciarán Smith.

The helicopter crashed over three weeks ago off the Mayo coast.

Search teams also looked for debris from the helicopter that crashed off Blackrock Island.

Garrett Morrison from the RNLI described the extent of today's search. 

“We have a very concentrated search area and it is very closely coordinated by the Coast Guard as well,” he said.

“That combined with the request for every mariner to keep a sharp lookout and report anything to the Irish Coast Guard should really help.”

He said the RNLI is hopeful the operation will benefit from today's good weather.

“It is a big push on to try and cover a really huge area with a view of trying to recover anything,” he said. “It is a request from the local fishing organisations and the Irish Coast Guard to do one massive big sweep now that the weather is good today.”

The search comes after Orla Smith, the sister of missing winch man Ciarán Smith, issued a fresh appeal for help with the search during the week.

Speaking to Newstalk Breakfast on Tuesday, Orla said the family wake up “a little bit of hope” every day that the crew members will be found and, “that we are going to get him home.”

The search zone has been divided into grids, with inshore boats working closest to the coastline and bigger vessels further out to sea.

It is estimated the fishing vessels will cover around 1,000 square miles in total.