When a plane is due in, in brief

ETA

Think of the three-letter abbreviation pilots use to say when they’ll touch down.

This clue plays on the phrase "due in," meaning when something is expected to arrive. "In brief" hints that the answer is an abbreviation, so instead of spelling out "estimated time of arrival," you use the three-letter shorthand. The answer is "ETA," a common term in travel and logistics for when a plane (or any vehicle) is scheduled to land.