Michigan officials said they would have propane supply security with trains and storage available if Enbridge Inc. shuts down deliveries in May on Line 5, the Canadian oil and natural gas liquids (NGL) system.

Line 5 flows 540,000 b/d, including 75,000 b/d of propane for about 55% of Michigan needs, led by two-thirds of requirements in northern parts of the state. The line also delivers NGLs to Ontario and Quebec. 

About half of the fuel supply at the Detroit airport is refined from oil delivered by the 68-year-old pipeline. Canada’s biggest airport in Toronto also relies on the endangered pipeline for all of its fuel.

However, Michigan Gov. Gretchen Whitmer sent industry “clear market signals” to devise alternatives to Line 5, according to the Michigan Public Service...