In the North American Game, came a mod possibly take a look at the Fort Lauderdale to San Antonio Route. Only one airline is flying it, but the Route Planning makes it look like two companies fly the route? How is this possible?
There is a bug forum.
But if the pie chart shows one airline, but the route planning shows two, odds are that the 2nd airline has just started flying the route, or has the only plane flying it in C-check, or maybe even grounded. So while they have a route scheduled, it hasn't actually sold any tickets in the past week or two, and so doesn't appear on the pie chart.
The other airline could also have been fired all their staff.