The Airship has missions that unlock based on your Commander level. Once you’ve beaten a mission, you can complete them again instantly, up to twice per day for free.
If you reach certain VIP levels (4, 7, 10, 12) you can refresh the missions to complete them even more times. The maximum is 5 per day, per Airship type. Each refresh costs Diamonds.
There’s 3 different types of missions, with 3 rewards – Gold, Ore, & Irobots.
The gold one is mostly useless and not worth spending any Diamonds on to refresh, however the Ore and Irobots can be very useful.