Raptors, they said, were essential replacements for the aging US aircraft fleet.
他们说，正在老化的美国飞机机群必不可少的替换物就是猛禽战斗机。
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The aging of the domestic fleet of about 237 million vehicles has been made possible by cars that are more durable and can be repaired more easily than in past recessions.
Not all of these problems have been due to the agingfleet, as many were signals to NASA that their continuing role in the cover-up over the presence of Planet X was not appreciated.