The blasts tore through the departures area at Brussels airport, which is regularly patrolled by soldiers but does not have a screening area for passengers.
After exiting the metro or inter-city trains arriving at the airport, passengers walk to an atrium where a three-level lift takes them either to the departures or arrivals area. To enter the departure area, passengers only have to scan their boarding passes before proceeding to security.
At rush hour, these areas, including the ticketing desks, can easily back-up, something the attackers clearly took advantage of as one of the bombers appeared to have detonated their device in exactly that vicinity.
In the Brussels metro however, the only security is the occasional police or group of soldiers at various entry points.
"This is what makes planning for these attacks so difficult," Hoffman said. "You might place security at the central train station but there are still a cornucopia of different areas that are open to attack across the city." In 2011, a suicide bombing carried out by Islamic militants at the Domodedovo International Airport bombing used similar tactics - striking in the arrivals hall where there were no security checkpoints.
The explosions in Brussels comes just days after Belgian police arrested Salah Abdeslam, one of the suspected participants in the Paris attacks. The 26-year-old allegedly planned logistics for the cell that carried out the deadly siege in November and was likely a key leader in the group.
According to Hoffman, the attacks just four days following Abdeslam's arrest, indicates how entrenched his compatriots are in the region.
"Their leader was picked up and the network didn't crumble, they adjusted their plans and responded in in a pretty expeditious fashion," Hoffman said, though it is currently unclear if Abdeslam was directly connected to the new blasts. "It indicates their network and infrastructure is much deeper than people have assumed."