One week after Brussels was targeted by Islamist extremists, staff at the city's airport have returned to the site where 15 people died.

The employees are taking part in a series of test runs to see if the airport can resume some flights.

The airport's chief executive has warned it could take months to be fully operational again.

Meanwhile, Ryanair says all flights due to operate to and from Zaventem up to and including Friday April 1st will continue to operate from Charleroi airport.

"Customers booked to fly from Brussels should make their way to Brussels Charleroi, arrive at least 3 hours before their flight and allow extra time for additional security checks," it said.

Aer Lingus has extended free changes or refunds for guests travelling to and from Brussels up to April 8th.

We've extended free changes/refunds for guests travelling to/from #Brussels up to 8 April. Change online / +353 18868989 / US (800) 585-0672

— Aer Lingus (@AerLingus) March 29, 2016

A total of 35 people died in suicide attacks at the airport and at a metro station in the city last week.