The US Department of Transportation is investigating possible deceptive practices in airline loyalty programs after federal lawmakers raised concerns about how companies are calculating points and rewards. DOT says it is planning “to carefully review complaints regarding loyalty programs and exercise our authority to investigate airlines for unfair and deceptive practices that hurt travellers as warranted.”

The spokesperson said agency officials are actively meeting with US airlines and gathering more information about the issue. Airlines for America, which represents the largest US carriers, declined to comment.

The department is stepping up its scrutiny after two US senators asked the agency and the Consumer Financial Protection Bureau (CFPB) about the steps they’re taking to protect consumers from “deceitful marketing tactics” in frequent flyer programs.

In a letter sent to the Secretary of Transportation and CFPB director in late October, the senators pointed to reports that suggest airlines are changing points systems – and even devaluing points – to make it harder to achieve rewards. The letter said this can stem from unilateral contracts that allow airlines to make changes to their points programs without directly notifying consumers.

In October, Southwest Airlines lowered the requirement for the top levels of its frequent-flyer program to lure in travellers dissatisfied with other airlines that are making it harder to reach elite status.