Also known as Aerial Ace, Sky Patrol was a hot air balloon simulator and was the only Imagic title for the 2600 never to be released. The prototype for this game was shown at the 82 CES show, complete with a mock up of what the production box and label would have looked like. The picture on the label, displaying World War I vintage biplanes attacking a dirigible, is interesting as it shows more of what the final game would have looked like if it had been completed
As it stands, the game is playable but very incomplete. You start the game with a hot air balloon sitting on a launch pad in the middle of a field. You can launch the balloon by filling it with enough hot air, or land it by letting the air out. The amount of hot air in the balloon is directly controlled by how high the burner flame is, and the burner flame is controlled pushing the joystick up and down. The height of the burner flame is shown as a red bar at the bottom of the screen. The green bar displays the amount of fuel for your burner, which is slowly whittled away as you use your burner. Once the fuel has been completely depleted, your balloon can only hover a few feet off the ground and is completely at the mercy of the wind (so don't let this happen). If you find yourself having fuel issues, you give yourself unlimited fuel by putting the left difficulty switch in the B position. The blue bar doesn't appear to be functional, but is probably a distance or damage gauge. Pushing right and left will alternate the display between the gauges and your score.
Although you can control the altitude of your balloon by filling or letting the air out of your balloon, you have no direct control over the direction in which you move. This is where the wind and those little clouds come in. By moving around to different altitudes you can catch different wind currents and thus somewhat control what direction you're going. The direction and speed of the wind currents varies depending on the altitude (there are 9 cloud / wind levels in all), but you can tell which way the wind is blowing by watching which way the clouds drift. Remember that there is a slight delay between when you add or let air out of your balloon and when you change altitude, so plan accordingly.
According to programmer Brad Stewart, the original object of the game was to attempt to get your balloon from Point A to Point B in as fast a time as possible. However as time went on the design of the game changed into something a bit more action oriented. According to the new story line the player is now piloting a WWI observation balloon and trying to avoid being shot down by the German army. This prototype appears to be of the 'action' version of the game, rather than the earlier 'race' version.
As previously mentioned, the goal of the game is stop enemy troops without being shot down. Although several of the enemy troops are present in the game, they are completely harmless in this early prototype. As you lazily drift along you will see tanks and anti-aircraft guns that in the final version of the game would have fired on the player, forcing them to ascend upwards to safety. There are also factories, hangars, and trees to spot, but these objects will not attempt to fire on the player. There is also what appears to be a man waving his arms next to an odd object at the end of the course. It is unknown what this is supposed to represent, but it may be a landing zone. Spotting each object is worth a set amount of points, but if the ground is not visible when you first see an object you will not earn any points until you move off the screen and come back.
The final version of the game would also have introduced enemy planes, dirigibles, rockets, and possibly trains into the enemy mix, making the game far more challenging. However development of the game was stopped before any of these could be implemented (although parts of the enemy dirigible graphics appear in the game code). Although Brad's original vision for Sky Patrol would have probably gotten the cold shoulder from the gaming public (hot air balloon racing isn't exactly mainstream), the action oriented observation balloon version might have been quirky enough to be a niche success.