Brussels' Zavantem airport may reopen later today - if it passes a security test.
The trial involving hundreds of staff coincides with an emergency security summit of aviation experts in the city.
It's just over a week since Brussels main airport was attacked by two suicide bombers.
The Department of Foreign Affairs is still advising any Irish citizens traveling to Belgium to remain vigilant and exercise extreme caution.
All Ryanair flights to/from Zaventem airport will be diverted to Brussels Charleroi until tomorrow.