The US Dept of Transportation is increasing both its surveillance of online advertising for Airline related businesses.
Indeed there is quite a lot of legal constraints on what you can and cannot do/say.
The DoT has just fined Frontier Airlines for a transgression.
Last month several online websites were fined.
And don't forget that the cash strapped US States are also getting into the act.
you have been warned. Comply with the letter and the spirit of the law