When you consider Fred's body weight, his equipment, food, clothing, etc., carrying him added at least 300 pounds to Amelia's plane, or at least 50 gallons of fuel. Actually, they also used radio navigation and those 1930s radios were heavy beasts, so the weight penalty was probably a lot more than that.

Today, a GPS handheld weighing ounces has accuracy orders of magnitude better than any human navigator could achieve in a plane back in the 1930s. GPS is a wonderful tool, almost certainly invented by men so they'd never have to ask for directions again.

Now, if only Steve can stretch his fuel supply. Doesn't seem too likely, though.