The search team operating off Blacksod Bay in Mayo say they have successfully mapped the ocean floor around the suspected crash site for Coast Guard helicopter Rescue 116.
They took advantage of a lull in the high ocean swell at the weekend and completed the necessary preparation for the next stage of the operation.
The Coast Guard's Declan Geoghegan said that they have made significant progress.
"All the work that we set out to do in terms of the preparatory work for the launch and the main rescue mission has been completed," he said.
"It's just weather dependent now. At the moment the forecast doesn't look great, I'm mainly talking about swell in that area."
It comes as Taoiseach Enda Kenny is due to meet with the families of the 3 missing crew today.