The City of Derry Airport reopened yesterday after officials approved new passenger-safety measures.
A British Airways (BA) flight to Dublin was first to depart after the four-day closure.
Other services by BA and charter flights also resumed yesterday, but Ryanair flights are not resuming until today.
There were calls for a full investigation to be made by Derry City Council, owner of the airport, into what was a major embarrassment.
The British Civil Aviation Authority (CAA) ordered the closure on Thursday following an audit of safety standards. Unsatisfactory repairs to an aircraft parking area and the lack of an effective bird-control plan were blamed.
Last weekend contractors carried out remedial work on the parking area, made improvements to the bird-management system, and carried out minor drainage improvements adjacent to the runway.
A joint inspection of the work by the CAA and the airport authority cleared the way for the reopening.
Sinn Féin Derry City councillor Gerry MacLochlainn, a member of the council's airport liaison committee, pledged to have the affair investigated.
"It is now incumbent on Derry City Council and its airport committee to examine the causes of this crisis in an open and transparent manner in order to reassure the travelling public and to apportion responsibility for any failures."