The cheapest way to reach Brussels city center from the airport (BRU) in 2026 is by using the De Lijn or STIB public buses, which cost approximately €3 for a single journey. Specifically, the STIB Airport Line (Bus 12) is a frequent express service that reaches the European Quarter in about 30 minutes. While the train is faster (taking only 17 minutes to Brussels North or Central), it includes a mandatory "Diabolo" airport supplement, bringing the total cost to around €10.30. For the absolute lowest price, some travelers walk or take a short local bus to the nearby Zaventem village station to avoid the supplement, though this is cumbersome with luggage. Using a contact-less payment or a "MOBIB" card is the most efficient way to pay for any of these transit options in 2026.