Belgian investigators have plotted his route away using footage captured at a number of locations.
The key suspect, who has still not been identified, is seen walking to the nearby town of Zaventem, and then into Brussels, before all trace of him is apparently lost.

The "man in the hat" was originally identified as a possible third attacker when he was seen on CCTV from the airport alongside the two bombers who detonated their suicide belts.
- See more at: http://www.naijagraceblog.com/2016/04/brussels-suspect-tracked-on-cctv-after.html#more