Ukraine’s military commander in charge of the country’s drone warfare program urged the US and NATO countries alike on Wednesday to learn from Kyiv’s use of the technology on the battlefield so in the future there are not “hard questions from your children [about] when [their] father will come back.

The relentless strikes rely on a drone that costs as little as $50,000 to make—about as a BMW M Sport costs in India. The cost to shoot one down? Often more than a million dollars. As James Black of the RAND Corporation put it,