Orders for requisitioning aircraft came from the defence department, which invoked the Civil Reserve Air Fleet (CRAF) provisions created after World War II to access "commercial air mobility resources.” The program, arising from the Berlin Airlift, involves pledges by private airlines to loan aircraft to the Pentagon within 24 hours upon activation.

from Times of India https://timesofindia.indiatimes.com/world/us/pentagon-commandeers-commercial-jets-for-airlift-amid-continuing-crisis-in-kabul/articleshow/85537629.cms