In survey results published in 2016, J.D. Power ranked United Airlines dead last among the major North American Airlines. Alaska Airlines ranked first with a score of 751 out of a possible 1,000 points followed by Delta with 725 points, making Delta the best choice among American carriers for intercontinental flights. United Airlines was the worst-ranked major North American carrier with 675 points. Anyone who has been following the bizarre treatment that some passengers have received from United employees will not find that surprising.
The American Customer Satisfaction Index (ACSI) found similar results in 2017. It ranked JetBlue and Southwest as having the best customer satisfaction with scores of 82 and 80 out of 100 possible points. Alaska followed with 78 points. Among the majors, United again ranked last with 70 points, a slight improvement over its 68 points in 2016. Ranking below United were two smaller airlines, Frontier with 63 points and Spirit with 61.
For domestic flights, JetBlue, Southwest, and Alaska look like the best airlines to fly. For international flights, Delta and American appear to be the best choices in that order, although American ranked below average in the J.D. Power 2016 survey. There seems to be universal agreement that United, Frontier, and Spirit are airlines that are best avoided.