at command—said of smth. at one’s disposal (and ready to be used):
- A constant supply of hot water is at command over the whole house.
in command—
1. having the authority to command:
- Like all those who are seldom in command, the master was proportionally tyrannical and abusive.
2. having control over a situation:
- He was looking more relaxed and in command than ever before.
on command—at the order given:
- On command the mother ship would have oriented itself and determined when to launch its subsatellites.