Airlines selling flights in the US must include all mandatory taxes, fees and charges in advertised fares from Thursday.
New fare rules introduced by the US Department of Transportation (DoT) last year take effect this week, putting a stop to adverts showing fares without taxes and charges.
Carriers must also disclose baggage fees when displaying a fare for a specific route.
The US has had more lax fare rules than the European Union since 2008-09 when Brussels tightened its regulations.
US passengers will also be able to cancel a payment without penalty within 24 hours of making a reservation, so long as they book at least a week before departure.
British Airways reportedly led the way in incorporating taxes and fees in fares in the US this month ahead of the January 26 deadline, employing the slogan: “What you see is what you pay.”
US carriers opposed the rule change, with a spokesman for industry group Airlines for America saying: “It will change the way airlines advertise.” He suggested carriers would advertise a range of prices on a route rather than a specific price.
The DoT has said it intends to take further action to ensure the transparency of fares.
The Department fined two airlines this month for violating price advertising rules in advance of the change. Korean-based carrier Asiana Airlines was fined $70,000 (£44,000) and Lot Polish Airlines $60,000 (£38,000).