Going by airplane is the fastest method for traveling.
Literal
Airplane [by-で] go [nominalizer-の] [subject-が] travel [purpose-のに] most fast method [copula-です].
Constructs a superlative comparison: 一番早い方法 ('fastest method'). ~のが marks the nominalized phrase as subject, and ~のに marks purpose: 'for the purpose of traveling.' Adding 方法 ('method') and polite です makes this clearer and more formal.