Holland’s K.L.M. Lines, restored to prewar strength, is already giving U.S. lines plenty of competition.

On the world’s airways, one fact was plain: the Air Age needed a lot of supercharging from state subsidies to maintain flying speed. Because of subsidies, free-enterprising American-flag lines, once way ahead, could now see a handful of foreign lines, state-supported in varying degrees, creeping up on their tails. On…