The first passenger flight has left Brussels Airport since it was closed after the suicide bombings on March 22 which blew up its departures terminal.
A Brussels Airlines flight heading to the Portuguese city of Faro has taken off from the airport, one of three services scheduled for today.
Airport chief executive officer Arnaud Feist said the flights leaving today were "a sign of hope" that even partial passenger service could resume so soon following "the darkest days in the history of aviation in Belgium".
The airport has been shut since suicide bombings at the hub and in the Brussels subway killed 32 victims and wounded 270. The attacks were claimed by the Islamic State group.
Security at the airport was tight on Sunday with completely new check-in procedures for passengers.
Other planes scheduled to leave included Brussels Airlines flights to Athens, Greece, and Turin, Italy.
Mr Feist also thanked all employees for their courage.
"We are more than an airport ... We are a family more bound together than ever," he said at an airport ceremony on Sunday.
Damage to the airport was extensive when double suicide bombs exploded near its crowded check-in counters 12 days ago, killing 16 victims and maiming people from around the world.
Another bombing that day on a Brussels subway train killed 16 other people.
Mr Feist said Belgium's biggest airport should be back to about 20% of capacity on Monday and able to process 800 passengers an hour.
New security measures at the airport aimed to minimise the chances of any repeat attacks.
Police on Sunday conducted spot checks of vehicles before they arrived. A large white tent was set up outside the terminal to screen travellers' IDs, travel documents and bags before they were allowed to enter the building.
A drop-off parking area outside the terminal was closed down and authorities said there would be no rail or public transport access to the airport for the foreseeable future.
The bombers entered the check-in area with suitcases packed with explosives and nails, and the resulting blasts collapsed the airport's ceiling and shattered windows.
The attacks have prompted a wider discussion among aviation authorities in many countries over whether to impose routine security checks at the entry to airport terminals.