A 90-minute power cut disrupted flights at Brussels Airport early on Friday, with passengers unable to check in and board planes.
Power went off around 6 a.m. (0400 GMT) in a departure area that was fully restored to operation last week following a twin Islamic State suicide bombing on March 22 that killed 16 people. A further 16 were killed by a bomb on the Brussels metro.
Although power was restored after about 90 minutes, some flights were delayed as passengers were still in long queues waiting to check in, a spokeswoman said.
The airport said it would take a few hours before normal operations resumed, with late departures but so far no cancellations.
Brussels airport was also forced to delay a planned news conference to present its 2015 results.