Squadrons was the original rules in John Stanoch's "Blue Sky" series and, I believe, there were some changes that were made between it and the later rules such as Red Sun/Blue Sky and the like-I have Squadrons but have not played it and so am not exactly sure what the differences, if any, are. Squadrons was the original and consisted of rules and aircraft cards containing the maneuver and other stats for the aircraft covered by the rules. Inasmuch as the maneuver numbers and maneuver rules are the core of all of John's rules, you will need both. The other rules in the Blue Sky system (except for Black Cross/Blue Sky) also consisted of rules and stats cards.
Squadrons covered the Battle of Britain, and has been replaced by John's Black Cross/Blue Sky set, which contains, among other things, aircraft-shaped cardboard counters in place of miniatures and flight stands-and a paper hex sheet-so it contains all you need to play the game. Black Cross/Blue Sky was a bit expensive for what it was and when it was released, a followup for early war in Poland may have been released but, AFAIK, that was the last.
Inasmuch as Squadrons was released in 1995 a copy may be hard to find… The last I knew (about 5-8 years ago) the Griffon Bookstore in South Bend, Indiana griffon-bookstore.com had 2 or 3 copies, but that's been a long time ago. They also had a few copies of some of the other Blue Sky rules, e.g. Red Sun/Blue Sky and Red Star/Blue Sky, but as I say it's been a long time since I saw them there.
As Sundance said, the Blue Sky system, uses hexes for movement, albeit at one time John Stanoch sold plastic or plexiglass hexes to use as measuring or maneuver "rulers" so you could play the game without a hex mat. Essentially you would use the "hexes" somewhat like the cards in Wings of Glory. I bought some of John's hexes but never played with them so I don't know how playable they were-I imagine they would add a bit of friction and delay to the game, but don't know for sure.
Also as Sundance said, the system uses altitude as an essential part of movement and maneuver, so flight stands with some sort of altitude measurement are essential to play the game.
For those unfamiliar with John's Blue Sky system…..
The core of the system is the interaction between movement and maneuver; in the basic game planes are allowed 4 maneuvers-slip, turn, half-roll and half-loop. Each maneuver is assigned a number, and that number is the number of hexes of straight and level flight the aircraft must move (can be accumulated over more than one turn) before the aircraft may perform the maneuver. This mechanism forces the player to space out his maneuvers.
So, for example, in Squadrons a Bf 109-E has a level speed of 6 hexes, a turn number of 3, a slip of 3, half roll of 6, and half loop of 5. BTW, the level speed of 6 is an absolute distance, but the 109 also has a brake factor and so the 109 in level flight can go full distance of 6, brake for 1 and go 5, or brake 2 and go 4 hexes. The number of accumulated hexes (we referred to it as "impetus") resets to 0 with every maneuver, which acts as a spacing mechanism.
So if a 109-E is in level flight and has no accumulated impetus (in our example it finished last turn on a maneuver, there are some limitations on this) must go at least 3 hexes of level flight before it may perform a slip or turn, or 5 hexes before it half-loop, or 6 hexes before it may half-loop. In our example, the 109 may fly 5 hexes forward (impetus at zero at beginning of turn in our example) then half-loop (invert the plane in the 5th hex and reduce altitude one level-actually the speed if performing a diving half-loop would be 9 hexes while a climbing half-loop would have a speed of 4 but I-incorrectly-use level speed to simplify the example) and fly one more hex inverted to accumulate 1 hex impetus. The next turn the 109 could continue inverted for another 5 hexes and then half-roll (the maneuver number for the half-roll is 6, but the 109 had 1 accumulated hex of impetus carried over from the prior turn). Due to the half-roll the 109 inverts again, so it is now right-side-up, and still has one hex of movement-it could, of course, brake and end turn in place-or use its remaining hex of movement and accumulate a hex on impetus (remember, impetus reset to 0 when the 109 did the half-roll.
IMHO, John's mechanism for accumulating impetus and spacing maneuvers is brilliant. Once you understand the way the system works, movement and maneuver are very simple and can be done quickly without referring to charts or diagrams. The only thing you need to know are the various movement and maneuver numbers. Altitude adds a minor degree of complexity-level speed, climbing speed and diving speed are different and some maneuvers can't be combined with climbing or diving; flightier typically can climb one level a turn while bombers can take 3 or 4 turns to climb a level. Diving varies a bit in individual cases, but isn't complicated.
Anyway, as I say I find the system to be simple and elegant, and it's easy to control and maneuver a vic or schwarm of aircraft or more. On the other hand, while I find the system simple, others sometimes have problems envisioning the interactions of the movement and maneuver components and prefer other rules. My local group, for example, had problems understanding the system and greatly preferred other rules-horses for courses, I guess.
BTW, I have simplified things a bit in my examples-some noted specifically-but they generally are correct and give the flavor of the system. If you have any more questions I'd be happy to provide whatever info I can. As I said, I think the system is brilliant, and don't understand why it isn't played more.
makes flight stands for 1/300 scale aircraft.
