AdvertisementThe Wall Street Journal reported last week that United CEO Scott Kirby personally called Delta CEO Ed Bastian last year to pitch a merger between the two airlines. This came before Kirby's already-known approach to American Airlines, which rejected him outright and said so publicly. Delta and United together control something like half the domestic aviation market. When the plane makers stop competing, the airlines that depend on them inherit the dysfunction, and so do the passengers. Some will argue, reasonably, that airlines are a scale business, that bigger carriers find real efficiencies in maintenance, crews, hubs, and aircraft purchasing.