United is the latest carrier to heap pressure on Spirit Airlines.
On Thursday, United announced frequency increases on 16 routes beginning Jan. 6, as well as the launch of two new routes -- all routes that are operated by Spirit.
The move comes less than a week after Spirit once again entered Chapter 11 bankruptcy restructuring, having failed to achieve financial stability from the restructuring it exited in March.
It also follows a similar announcement by Spirit's discount competitor Frontier last week, which will begin service between November and February on 18 routes served by Spirit.
In a prepared remark, United senior vice president of global network planning Patrick Quayle positioned the new scheduling as an act of benevolence.
"If Spirit suddenly goes out of business it will be incredibly disruptive, so we're adding these flights to give their customers other options if they want or need them," he said.
The comment, which was included in a United statement, prompted a sharp retort from Spirit vice president of communications Duncan Dee.
"While we appreciate the obsession certain airline executives have with us, we're focused on competing and running a great operation," Dee said. "Suggesting anything else is wishful thinking on the part of a high-cost airline looking to eliminate a low-cost competitor so they can fulfill their ultimate goal of charging American travelers the highest fares possible to visit the people and places they love."
United will add one daily frequency to its schedule from Houston Bush Intercontinental to Orlando, Las Vegas, New Orleans, Atlanta, Baltimore and Miami. It will also add one daily frequency between Chicago O'Hare and Orlando, Fort Lauderdale, New Orleans and Las Vegas. From Newark, it will fly once more per day to Fort Lauderdale and Orlando. And United will also increase its scheduled by one flight daily between Las Vegas and Los Angeles.
United will also add three frequencies per week on service between
Houston and Guatemala City and San Salvador, as well one additional
weekly frequency on Houston-San Pedro Sula, Honduras.
The airline's two newly announced routes connect Newark to Columbia, S.C. and Chattanooga, Tenn. United previously flew Newark-Columbia between 2012 and 2014, a route that became known as "the chairman's flight" after it was at the center of a corruption scandal involving David Samson, who was then the chairman of the Port Authority of New York and New Jersey, which controls Newark Airport.
Five of the routes on which United will add frequency are also routes that Frontier is launching. Those include the three routes between Houston and Central America, which are the first for Frontier in that region from Houston.