Rene Laumann's childhood dream of being a professional pilot did not come true, but flying became his hobby and is now part of a humanitarian mission.

After Russia invaded Ukraine on Feb. 24, Laumann started flying small planes on 3-1/2 hour trips to Poland to deliver medical aid to war victims and transport refugees with special needs to Germany.

Over 4.6 million people have fled Ukraine to neighbouring countries since Moscow launched what it calls a "special operation" - the biggest attack on a European state since 1945. More than half of those have gone to Poland, according to United Nations data.

Laumann, 35, is among a group of amateur German pilots who formed Ukraine Air Rescue, a humanitarian initiative using their planes. Five of them regularly fly between the German city of Mainz near Frankfurt and Rzeszow in Poland.

"We have already carried out 20 flights and we transported around 20 people," Silke Hammer, a spokesperson for the group, said in an interview. "Today, we are taking a stroke patient to Cologne."

The pilots transport medical supplies for cancer patients, first-aid kits for bone fractures, styptic drugs and medicines that need to be refrigerated, such as insulin.

At Rzeszow airport, the pilots take on Ukrainian refugees with special needs to an airport near the German city of Bonn to receive further support.

"These are passengers who can't be easily transported overland because they have serious health problems. Some of them are probably children," Laumann said.

"You can never be 100% sure about what to expect. You just have to see."