American Airlines Group Inc. priced a $10 billion bond and loan offering backed by its frequent-flyer program as investors clamored for the protection provided by the special structure.

The carrier received around $45 billion in orders on the total $10 billion deal, according to people with knowledge of the matter, who asked not to be named discussing a private transaction. Roughly $30 billion of the demand was for the bond portion.

On Wednesday, the company boosted the size and cut borrowing costs on the debt sale, making it the largest ever by an airline. American increased the bond size by $1.5 billion total. The bond tranches, which mature in five and eight years, yield 5.5 percent and 5.75 percent, respectively—lower than initial discussions in the 6 percent range.