Battle Group 2

Cannon kills done with Iowa will not qualify. You must use missile-launching ships to farm the kills. Play level 25 (the level before the final area) with Arsenal and a large number of Hyper Times. This level features a total of seven or eight missile launching planes that resemble passenger aircraft. Most of the time the enemies appear in large groups, allowing for many hits for each Hyper Time. It is possible to get approximately 200 hits per playthrough of this level in exchange for five Hyper Times. To gain Hyper Time, do a complete playthrough with Iowa and the aircraft carrier. You can get about 120 oil barrels per level if you score 100% accuracy.
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This may take some time, because Skyhawks are the rarest enemy. Play level 17, which features twelve Skyhawks at the start. Restart the level after destroying them. Repeat the process as many times as needed.