The people who are investigating the crash of Swissair flight 111 say no plane should fall out of the sky because of a spark, so, Canada's Transportation Safety Board wants all flammable materials removed from airplanes.

The passenger jet caught fire nearly three years ago while over Nova Scotia and crashed into the waters off Peggy's Cove, killing all 229 people on board.

Since the disaster, a series of safety recommendations have been made, but the most far-reaching were issued by the Transportation Safety Board on Tuesday.

"A specific spark, whatever the location, should not bring down an airplane," says Vic Gerden, the TSB's chief investigator. "There should be defences in place that prevent that."

Because of stringent fire tests on seat cushions and cabin features, the most combustible items on planes are behind the cabin walls, things like insulation blankets, and even tape.

Gerden says a fire couldn't continue if there was nothing there to burn.

The board is also recommending tougher tests for wiring, and an evaluation of emergency oxygen systems for fear they could leak and feed a fire in progress.

The TSB does not yet know what specifically caused the crash of Swissair flight 111 saying it was clearly a series of problems, not just one thing that went wrong.