Drag a plane over to the trash can icon to throw it away. You’ll get some coins when you do this, but they won’t be enough to really make a dent in your overall money earnings. The main use for trashing a plane is when you run out of spots, but you also have no more combinations left to make. This doesn’t happen often, but it happens often enough for it to be an issue later on in the game, when you’re into the level 20 and above planes.
There are a total of 40 planes that you can unlock in the main airport area. If you go to the plane store on the iOS version of the game at the present moment, you’ll count a total of 30 planes and silhouettes of unavailable planes, but on Android, there are 40 planes available. The update will come soon to the iOS as well, and give you those ten extra planes.
The Star Trek quest comes around every once in awhile, but you have to wait for the developers to initiate the event. When the event is initiated, you’ll be able to enter the Star Trek area and complete quests there, as well as unlock a total of 15 new spaceships. Your gems are shared between both games, but your secondary currency (propeller coins in the main airport and circuit boards in Star Trek) are unique to their own games.
The weekly membership can speed things along significantly in the game in many ways. All of the involuntary ads will go away, but the voluntary ad bonuses will still stick around. Your offline earnings will be boosted by 20%, and the speed of the planes will go up by 50%. You’ll add two more parking spaces than you would have otherwise in your apron at any given point in time, as well as two more chevrons on the track, so that you can place the planes. You’ll also get ten gems per day.
The coin calculation will show in the top left corner of the screen, and will reflect the last runway boost that you bought – for example, after buying the first runway boost, it will say Coins x1.10, and after the second one, it will say Coins x1.20. When you take the 5x coin bonus, instead of the coin counter saying Coins x5.10 or 5.20, it will be five times whatever your current coin count is without the boost. So at x1.20, it will say Coins x6.00 with the 5x bonus.
As far as the quests go, regarding the quests that require you to have a specific number of planes, the planes that are opened up from either a gold box or a standard box won’t count. The only planes that will count towards these quests are the ones that have either been purchased out of the store, or planes that are the result of merging two planes one level down. The source of the pre-merge planes doesn’t matter, though.