As the most recent armed conflicts suggest, air warfare has known an exponential growth. This is caused by several factors: suffice it to mention the swiftness of the intervention, the possibility to strike remote targets (thanks to in-flight refuelling) and to minimize the attacker’s casualties (thanks to the aircraft’s limited vulnerability against an enemy with poor technology and to the use of unmanned aerial vehicles). Notwithstanding this increasing recourse to military aerial operations, the law of air warfare has not been completely codified yet. Taking the existing provisions governing aerial bombardment, and more particularly the principles of distinction and proportionality, into account, the present article explores how the concept of “military objective” in air-to-ground bombardment has evolved during the most recent armed conflicts which involved the use of air power, namely Operation Desert Storm and Operation Iraqi Freedom in Iraq, Operation Allied Force in Kosovo, and Operation Enduring Freedom in Afghanistan. The article also focuses on the most recent military documents and manuals on air warfare, with particular regard to those of the United States.