Iran was about to retaliate for the American drone strike that had killed Iran’s top military commander, Gen. Qassim Suleimani, in Baghdad five days earlier, and the military was bracing for an American counterstrike. The armed forces were on “at war” status, the highest alert level.

But in a tragic miscalculation, the government continued to allow civilian commercial flights to land and take off from the Tehran airport.

Gen. Amir Ali Hajizadeh, commander of the Guards’ Aerospace Force, said later that his units had asked officials in Tehran to close Iran’s airspace and ground all flights, to no avail.

Iranian officials feared that shutting down the airport would create mass panic that war with the United States was imminent, members of the Guards and other officials told The Times. They also hoped that the presence of passenger jets could act as a deterrent against an American attack on the airport or the nearby military base, effectively turning planeloads of unsuspecting travelers into human shields.