Almost 16 months after the merger creating American Airlines Group Inc., US Airways’ “Cactus” call sign is poised to disappear.

That may be the most-tangible aspect of the milestone that awaits American on Wednesday, when it gets a so-called single operating certificate from U.S. regulators. The move clears the way for the last phase of a deal that closed in December 2013: moving to a unified reservation system in the fourth quarter.

Receiving the certificate “really isn’t noticeable from a customer perspective, but it’s quite significant internally,” said Bob Mann, a former American executive who now runs aviation consultant R.W. Mann & Co. “It covers every maintenance procedure, every training procedure, every operational procedure and every safety-oriented procedure.”

“Cactus” will be retired for flights starting at 2 a.m. Dallas time on Wednesday. US Airways crews use that designation to identify their planes to air traffic controllers — a nod to the desert city of Tempe, Arizona, that was home to US Airways and one of its predecessors, America West Airlines. Fort Worth, Texas-based American announces its aircraft as “American.”

While the US Airways name isn’t going away yet because fliers can still book trips on that website, U.S. Federal Aviation Administration clearance to run as one carrier means American will be able to reap more of the promised $1 billion in deal savings. Among other things, American will be able to have mechanics share parts between the two divisions and put airport operations in the same place.

‘Mirror Image’

The single operating certificate “is really the prerequisite for anything to come,” Chief Operating Officer Robert Isom said Monday in an interview. “You have to create mirror images of the companies in terms of operating policies and procedures long before you can bring people together.”

It also paves the way for the phase of merger integration that holds the largest risk of disruption for passengers: the cutover to a common reservation system. That change is supposed to occur in the fourth quarter.

About 700 American employees were involved in the SOC preparations, which included training for more than 110,000 workers in 54 countries. The two airlines’ procedures for handling dangerous goods were the most difficult to align, said Kevin Brickner, a vice president in the technical operations group.

“There are no light-switch type transitions for virtually anything but the call sign,” Isom said. “The SOC date is really a recognition that everything has come together.”

American was the third-biggest U.S. airline when it left bankruptcy as the merger closed, while US Airways was No. 5. The combined company kept the American brand as Chief Executive Officer Doug Parker moved over from US Airways and brought most of his leadership team with him.

American combined its frequent flier program with that of US Airways last month, and co-locating and rebranding airport facilities will continue through this year and next. American also is working to paint all US Airways aircraft in American’s livery by 2017, Isom said.

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This article was written by MARY SCHLANGENSTEIN from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: A US Airways Embraer ERJ-190 jet descends for landing at Philadelphia International Airport in Philadelphia, Pennsylvania on December 9, 2013. Mark Makela / Reuters