How do you get enough money to buy expensive buildings?

as an example....mission control center level3 costs 400,000 coins. Incoming planes and my own planes won't provide enough coins to reach such a number quickly.
Even with spave missions (blue missions for example) only provide 10,000.

So...what's the trick to earn coins in a quick way?

Also...how much does a red space mission provide in coins, Tokens etc?

@TallguyNL

• Flying frequently and clicking on your commercial buildings 24/7 is the basic way of making money.
• You need to calculate the best buildings that generate coins for you (it depends on what is available at your level and how frequently you play)
  
• Completing collections also earns you money, so fly with a purpose, not just randomly.
  
• When you have a quest, do not complete it as soon as you can, because the more collections you complete, the more money you earn. Drop rates decline after you complete the quest.
• Joining a Green / Blue / Red QL party earns you a lot of money only because you can do like 20 launches in an hour instead of the regular once every 24 hours. You should try to join it whenever a QL party is announced on the forum.
• Bonuses such as Incovertible coin, Business class and Sky Captain multiplies the coins you earn. Use it to use well and plan your flights (best to activate Business Class in the morning, before clicking on your incoming planes, also when joining a QL party).

You must have patience to play this game. It is set to be difficult on purpose. If you neither have the time or patience, you have the option to buy coins or greenies.

Thank Bali Hi