A United-American tie-up would be the most significant airline merger in a decade and further tighten the grip of legacy carriers. But approval by regulators seems like a long shot.

Delta's language shift, from "goal" to "aspiration," may sound like semantics, but it signals a broader retreat from hard climate commitments at a moment when the airline industry's 2050 net-zero pledge is already under strain.

Qantas is making the best of a bad situation. The problem is the situation isn't getting any better.

A tie-up between United and American would create the largest carrier in the U.S. and have major ramifications for competition in the airline industry.

Despite rising fuel costs, Southwest CEO Bob Jordan said the carrier's business model keeps its costs well below the competition.