Dr McDonnell said he understood the planning application had been given the full support of Environment Minister Edwin Poots.
He said there needs to "absolute transparency" surrounding any decision on the implications of the runway extension.
"The necessary public confidence in the political process can only be achieved if that decision, one way or the other, is made after a full public inquiry," said the South Belfast MP.
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Dr McDonnell suggested the decision was made against the backdrop of Northern Ireland having no official aviation strategy.
"It is incredible that in terms of the economic blueprint for Northern Ireland we are still waiting for such a key business and tourism plan," he said.
"My information is that the Minster will make a public announcement by the end of the month in relation to the airport runway.
"The Minister and his department will try and sell this scheme by stressing that it will 'only be an additional 500 metres' of tarmac."
The proposed runway extension project has been described by the management of the city airport as a vital part of its development plan.
The project has received significant public support from Ryanair boss Michael O’Leary, one of the main airlines currently using the airport.
(PR/KMcA)
