What Does It Mean To Say Us Airways Flight 6558 Is 'operated By United'?

With codeshares and alliances and such in order to connect travelers to as many destinations as possible without sending up half empty planes, there are new partnerships between airlines.

In your case the wording usually this simply means a codeshare where you might have one leg of the flight on another airline's plane. The flight number for your ticket would be the US Airways number and United's but the plane itself is a United Airlines' plane.

Everyone benefits except the crew that didn't work that combined flight.

While the terms are sometimes used interchangeably, codesharing is one of the benefits of airline alliances. Codesharing is the practice of one airline putting its two-letter code on a flight operated by another airline. The first airline can market and sell seats on that flight, even though its planes are not operating on that route. These agreements give airlines the ability to sell tickets to more destinations, while the benefit for travelers is that they can fly a multiple-leg trip as if they were using a single carrier, when in fact they may be taking two or more airlines' planes.