The Government Learjet has been used to take a critically ill two-year-old boy for a life-saving liver transplant in the UK.
The Air Corps also carried a one-month-old baby from Crumlin Children's Hospital for treatment at King's College Hospital in London.
The two Air Ambulance missions took place within half an hour of each other, at 12.30pm and 12.55pm on Thursday.
Both aircraft were fitted out with specialist LifePort facilities and carried HSE staff and landed safely at RAF Northolt, London.
A Defence Forces spokesman said the Learjet had been prioritised over commercial flights and was the first aircraft to leave Dublin airport following the earlier closure due to snowfall.
The toddler will also undergo his surgery in King's College Hospital.
A total of 65 Air Ambulance missions have been carried out by the Air Corps so far this year, transporting neo-natal, transplant and other seriously ill patients to medical facilities in the UK and Ireland.
The figure includes an operation carried out flying in reduced visibility due to snow using Night Vision Goggles earlier this week.
Meanwhile, a Defence Forces spokesman said the Air Corps had flown in excess of 6,200 missions so far this year.
"Some 280 maritime patrols were also carried out, safeguarding Ireland's interests at sea in conjunction with the Naval Service," he said.