OTTAWA -- After a false start, Prime Minister Justin Trudeau departed Saturday night for Brussels to finally sign Canada's controversial free trade deal with the European Union, days after it teetered on the brink.

Trudeau's plane returned to Ottawa about 30 minutes after it took off because of a mechanical problem involving the flaps, the Prime Minister's Office said in an email.

The plane's departure had already been pushed back some 90 minutes delaying Trudeau from getting to Europe to sign a trade deal that has been beset with delays.

The plane was airborne again late Saturday after a brief period on the ground in Ottawa.

Trudeau was expected to sign the Comprehensive Economic and Trade Agreement, or CETA days ago, but the Belgian region of Wallonia cast doubt over its future by opposing it. Wallonia held a veto over Belgium's ability to support the deal, which requires the approval of all 28 EU countries.

The tiny French-speaking region of 3.5 million people opposed the deal's investor protection provisions, taking up the cause of anti-trade and civil society groups, but Wallonia's concerns were finally addressed on Thursday.

The Prime Minister's Office says Trudeau spoke on Friday with European Council president Donald Tusk, who confirmed the texts of the deal, along with a side agreement known as the Strategic Partnership Agreement, have been approved for signature.

Trudeau was to meet with European Union leaders in Brussels on Sunday where they are to finally sign CETA, which was seven years in the making. He will also meet with Quebec Premier Philippe Couillard, who has already arrived in Brussels.

Canada's International Trade Minister Chrystia Freeland walked out of talks with the Europeans a week ago saying it appeared the EU was incapable of signing an agreement. She maintained Canada's work was done and it was up to the Europeans to remove the remaining roadblocks.

After almost a week of painstaking negotiations -- talks that forced Trudeau to postpone his travel to Europe -- the Walloons and the Belgian national government reached a deal.

The Walloons dropped their opposition following an agreement Thursday with the Belgian government that gave national and regional parliaments throughout Europe new powers over controversial investor protection provisions.

The new Belgian agreement essentially gives Europe's individual national and regional parliaments the ability to veto the investor protection provisions at a later date.

The agreement also calls for a review of the dispute settlement mechanism by the European Court of Justice.

A Canadian government official, who was not authorized to speak by name, said the Belgian agreement does not give any new powers, and are "just declarations."

The official said EU member states cannot pick and choose from parts of the agreement.

The official said the text of CETA has not changed since it was signed in February.

But at least one Canadian financial institution questioned the overall strength of the trade agreement.

In a research note to clients this past week, TD Economics said "uncertainty" still remains around CETA's ultimate fate.

"Should a revised dispute system not be agreed in the coming years, CETA may still be undone (remember that it would only take one member state rejecting the revised dispute system to make the entire agreement null)," the memo said.

The Wallonia parliament voted overwhelmingly to allow the Belgian national government to support the pact.

The Council of the European Union adopted a package of decisions on matters such as signing the agreement, its provisional application and requiring the European Parliament's consent to conclude the deal.