Denver-based Frontier Airlines has replaced its toll-free customer service phone number with a regular toll-charge line.
The move mimics a 2013 decision by the ultra-low-cost carrier Spirit Airlines to save money by passing on to customers the cost of the phone calls.
Frontier's move is no surprise considering that the same investors who for years financed Spirit bought Frontier Airlines in 2013 with plans to make it into the mirror image of Spirit.
Florida-based Spirit is known for super-low fares with a long menu of passenger fees, including a $10 charge to have an airport agent print out your boarding pass. Spirit also has the nation's highest rate of consumer complaints.
Why would Frontier want to follow Spirit's example?
It's probably because Spirit reported a profit margin of 21% in the most recent quarterly earnings, more than twice the average margin for the entire industry last year.