The United States could alter its decades-old North American Aerospace Defense Command deal with Canada should its government backtrack on the purchase of 88 Lockheed Martin F-35 fighter jets, the U.S. ambassador to Canada has warned. In the latest back-and-forth between the U.S. and Canada over the deal, Ambassador Pete Hoekstra cautioned that if Canada purchased fewer fighter jets, the U.S. would “fill those gaps” in security concerns. That could mean the U.S. would need to purchase more F-35