The colored airplane images are one way to quickly determine the general status of a flight.
A flight that has a status of "Delayed", "Cancelled", "In Air - Diverted", "Landed - Diverted", "In Air - Recovery", "Landed - Recovery", "No Takeoff Info - Call Airline", or "No Recent Info - Call Airline" will have a red airplane image next to it.
A flight that has a status of "Scheduled", "Departed", "In Air", "Landed", "Arrived", or "Expected" will have a green airplane image next to it.
A flight that has a status of "Past Flight" and "Flight Unmatched - No Status" will have a gray airplane image next to it.